$SIGI
Selective Insurance Group Inc Stock $sigi

$sigi Overview Financials Valuation SEC Filings Company Website

2020 Q1 Form 10-K Financial Statement

#000023055720000005 Filed on February 12, 2020

Income Statement

Concept	2020 Q1	2018 Q4	2018 Q3
Revenue	$664.8M	$643.0M	$664.5M
YoY Change	-4.88%	1.46%	6.95%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin	$12.00M	$3.400M	$7.500M
YoY Change	-25.47%	-90.63%
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$136.5M	$9.900M	$124.5M
YoY Change	5.26%	-28.78%	5.39%
% of Gross Profit
Operating Expenses	$641.3M	$584.8M	$591.3M
YoY Change	4.5%	4.52%	7.92%
Operating Profit
YoY Change
Interest Expense	-$7.600M	-$6.100M	-$6.100M
YoY Change	-33.91%	0.0%	0.0%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$16.00M	$52.14M	$67.13M
YoY Change	-78.29%	-23.5%	-0.27%
Income Tax	$761.0K	$6.400M	$11.70M
% Of Pretax Income	4.76%	12.28%	17.42%
Net Earnings	$15.24M	$45.76M	$55.44M
YoY Change	-75.16%	51.31%	18.66%
Net Earnings / Revenue	2.29%	7.12%	8.34%
Basic Earnings Per Share	$0.26	$0.77	$0.94
Diluted Earnings Per Share	$0.25	$0.76	$0.93
COMMON SHARES
Basic Shares Outstanding	59.67M shares	58.89M shares	58.84M shares
Diluted Shares Outstanding

Balance Sheet

Concept	2020 Q1	2018 Q4	2018 Q3
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$14.61M	$16.92M	$12.83M
Short-Term Investments
Other Short-Term Assets
YoY Change
Inventory
Prepaid Expenses
Receivables
Other Receivables
Total Short-Term Assets
YoY Change
LONG-TERM ASSETS
Property, Plant & Equipment	$80.06M	$65.25M	$64.23M
YoY Change	16.61%	2.02%	-3.19%
Goodwill	$7.849M	$7.849M	$7.849M
YoY Change	0.0%	0.0%	0.0%
Intangibles
YoY Change
Long-Term Investments	$6.842B	$5.961B	$5.861B
YoY Change	9.76%	4.85%	2.63%
Other Assets	$48.30M	$70.00M	$64.70M
YoY Change	14.73%	118.75%	22.31%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$8.975B	$7.953B	$7.987B
YoY Change	8.36%	3.46%	2.24%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$103.4M	$116.7M	$95.40M
YoY Change	-0.19%	-11.52%	-15.65%
Deferred Revenue
YoY Change
Short-Term Debt	$302.0M	$0.00	$0.00
YoY Change
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$417.8M	$118.0M	$107.5M
YoY Change	256.48%	-10.54%	-10.27%
LONG-TERM LIABILITIES
Long-Term Debt	$550.6M	$439.5M	$439.4M
YoY Change	0.09%	0.09%	0.09%
Other Long-Term Liabilities	$292.1M	$277.6M	$292.4M
YoY Change	15.23%	-1.42%	-9.84%
Total Long-Term Liabilities	$842.7M	$717.1M	$731.8M
YoY Change	4.87%	-0.5%	-4.13%
TOTAL LIABILITIES
Total Short-Term Liabilities	$417.8M	$118.0M	$107.5M
Total Long-Term Liabilities	$842.7M	$717.1M	$731.8M
Total Liabilities	$6.879B	$6.161B	$6.248B
YoY Change	8.2%	3.14%	2.22%
SHAREHOLDERS EQUITY
Retained Earnings	$2.083B	$1.858B	$1.825B
YoY Change	9.18%	9.41%	8.67%
Common Stock	$635.0M	$596.0M	$591.0M
YoY Change	4.9%	4.15%	4.22%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$599.8M	$584.7M	$584.5M
YoY Change	1.44%	1.13%	1.11%
Treasury Stock Shares	44.12M shares	43.90M shares	43.90M shares
Shareholders Equity	$2.096B	$1.792B	$1.739B
YoY Change
Total Liabilities & Shareholders Equity	$8.975B	$7.953B	$7.987B
YoY Change	8.36%	3.46%	2.24%

Cashflow Statement

Concept	2020 Q1	2018 Q4	2018 Q3
OPERATING ACTIVITIES
Net Income	$15.24M	$45.76M	$55.44M
YoY Change	-75.16%	51.31%	18.66%
Depreciation, Depletion And Amortization	$136.5M	$9.900M	$124.5M
YoY Change	5.26%	-28.78%	5.39%
Cash From Operating Activities	$39.32M	$162.4M	$200.2M
YoY Change	-15.7%	82.06%	2.77%
INVESTING ACTIVITIES
Capital Expenditures	$8.416M	-$4.900M	-$4.500M
YoY Change	5.8%	113.04%	-6.25%
Acquisitions
YoY Change
Other Investing Activities	-$307.4M	-$143.4M	-$186.5M
YoY Change	128.04%	171.59%	4.31%
Cash From Investing Activities	-$315.8M	-$148.3M	-$191.0M
YoY Change	121.28%	169.15%	4.03%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net	$6.928M
YoY Change	5.21%
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	$283.1M	-10.00M	-12.90M
YoY Change	215.71%	21.95%	38.71%
NET CHANGE
Cash From Operating Activities	$39.32M	162.4M	200.2M
Cash From Investing Activities	-$315.8M	-148.3M	-191.0M
Cash From Financing Activities	$283.1M	-10.00M	-12.90M
Net Change In Cash	$6.631M	4.100M	-3.700M
YoY Change	-203.53%	-84.17%	-294.74%
FREE CASH FLOW
Cash From Operating Activities	$39.32M	$162.4M	$200.2M
Capital Expenditures	$8.416M	-$4.900M	-$4.500M
Free Cash Flow	$30.90M	$167.3M	$204.7M
YoY Change	-20.12%	82.84%	2.56%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2018Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	5270798000	USD
CY2019	dei	Amendment Flag AmendmentFlag	false
CY2019	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2019	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2019	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2019
CY2019	dei	Document Period End Date DocumentPeriodEndDate	2019-12-31
CY2019	dei	Entity Central Index Key EntityCentralIndexKey	0000230557
CY2019Q4	sigi	Consolidated Net Worth Actual ConsolidatedNetWorthActual	2100000000	USD
CY2019Q4	sigi	Debt To Capitalization Ratio DebtToCapitalizationRatio	0.207
CY2019Q4	sigi	Line Of Credit Consolidated Net Worth Requirement LineOfCreditConsolidatedNetWorthRequirement	1400000000	USD
CY2019Q4	sigi	Line Of Credit Debt To Capitalization Ratio Requirement LineOfCreditDebtToCapitalizationRatioRequirement	0.35
CY2018Q4	sigi	Maximumexposuretocreditconcentrationriskofthe Companysstockholdersequityotherthancertain U.S.Governmentagencies MaximumexposuretocreditconcentrationriskoftheCompanysstockholdersequityotherthancertainU.S.governmentagencies	0.10
CY2017	sigi	Related Party Transactions Contributions To Foundation RelatedPartyTransactionsContributionsToFoundation	0	USD
CY2018Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	211657000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	227566000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	5879986000	USD
CY2018Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	2
CY2019Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	2
CY2018Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	360000000	shares
CY2019	dei	Trading Symbol TradingSymbol	SIGI
CY2019	dei	Security Exchange Name SecurityExchangeName	NASDAQ
CY2018Q4	us-gaap	Equity Securities Fv Ni Cost EquitySecuritiesFvNiCost	138114000	USD
CY2019Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	360000000	shares
CY2018Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	102848394	shares
CY2019Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	103484159	shares
CY2018	us-gaap	Costs And Expenses Related Party CostsAndExpensesRelatedParty	2000000	USD
CY2019Q4	us-gaap	Equity Securities Fv Ni Cost EquitySecuritiesFvNiCost	72061000	USD
CY2019Q1	us-gaap	Finance Lease Liability FinanceLeaseLiability	900000	USD
CY2017Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0
CY2018Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0
CY2019Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0
CY2017Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	5000000	shares
CY2018Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	5000000	shares
CY2019Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	5000000	shares
CY2017Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
CY2018Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
CY2019Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
CY2018Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2019Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2018Q4	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	9400000	USD
CY2019Q4	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	6400000	USD
CY2018Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	4500000	USD
CY2019Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	4400000	USD
CY2018Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	43899840	shares
CY2019Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	44023006	shares
CY2019	dei	Document Type DocumentType	10-K
CY2019	dei	Document Annual Report DocumentAnnualReport	true
CY2019	dei	Document Transition Report DocumentTransitionReport	false
CY2019	dei	Entity File Number EntityFileNumber	001-33067
CY2019	dei	Entity Registrant Name EntityRegistrantName	SELECTIVE INSURANCE GROUP, INC.
CY2019	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	NJ
CY2019	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	22-2168890
CY2019	dei	Entity Address Address Line1 EntityAddressAddressLine1	40 Wantage Avenue
CY2019	dei	Entity Address City Or Town EntityAddressCityOrTown	Branchville
CY2019	dei	Entity Address State Or Province EntityAddressStateOrProvince	NJ
CY2019	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	07890
CY2019	dei	City Area Code CityAreaCode	973
CY2019	dei	Local Phone Number LocalPhoneNumber	948-3000
CY2019	dei	Security12b Title Security12bTitle	Common Stock, par value $2 per share
CY2019	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2019	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2019	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2019	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2019	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2019	dei	Entity Small Business EntitySmallBusiness	false
CY2019	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
CY2019	dei	Entity Shell Company EntityShellCompany	false
CY2019Q2	dei	Entity Public Float EntityPublicFloat	4357013702	USD
CY2020Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	59670192	shares
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	20800000	USD
CY2018Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	37110000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	6095620000	USD
CY2018Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	5273100000	USD
CY2019Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	72937000	USD
CY2018Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	147639000	USD
CY2019Q4	us-gaap	Other Short Term Investments OtherShortTermInvestments	282490000	USD
CY2018Q4	us-gaap	Other Short Term Investments OtherShortTermInvestments	323864000	USD
CY2019Q4	us-gaap	Other Investments OtherInvestments	216807000	USD
CY2018Q4	us-gaap	Other Investments OtherInvestments	178938000	USD
CY2019Q4	us-gaap	Investments Investments	6688654000	USD
CY2018Q4	us-gaap	Investments Investments	5960651000	USD
CY2019Q4	us-gaap	Cash Cash	300000	USD
CY2018Q4	us-gaap	Cash Cash	505000	USD
CY2019Q4	us-gaap	Restricted Cash And Cash Equivalents At Carrying Value RestrictedCashAndCashEquivalentsAtCarryingValue	7675000	USD
CY2018Q4	us-gaap	Restricted Cash And Cash Equivalents At Carrying Value RestrictedCashAndCashEquivalentsAtCarryingValue	16414000	USD
CY2019Q4	us-gaap	Accrued Investment Income Receivable AccruedInvestmentIncomeReceivable	44846000	USD
CY2018Q4	us-gaap	Accrued Investment Income Receivable AccruedInvestmentIncomeReceivable	41620000	USD
CY2019Q4	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	823901000	USD
CY2018Q4	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	770518000	USD
CY2019Q4	us-gaap	Reinsurance Recoverables ReinsuranceRecoverables	573235000	USD
CY2018Q4	us-gaap	Reinsurance Recoverables ReinsuranceRecoverables	549172000	USD
CY2019Q4	us-gaap	Prepaid Reinsurance Premiums PrepaidReinsurancePremiums	166705000	USD
CY2018Q4	us-gaap	Prepaid Reinsurance Premiums PrepaidReinsurancePremiums	157723000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	6776000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	53540000	USD
CY2019Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	8797150000	USD
CY2018Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	7952729000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	77409000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	65248000	USD
CY2019Q4	us-gaap	Deferred Policy Acquisition Costs DeferredPolicyAcquisitionCosts	271186000	USD
CY2018Q4	us-gaap	Deferred Policy Acquisition Costs DeferredPolicyAcquisitionCosts	252612000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	7849000	USD
CY2018Q4	us-gaap	Goodwill Goodwill	7849000	USD
CY2019Q4	us-gaap	Other Assets OtherAssets	128614000	USD
CY2018Q4	us-gaap	Other Assets OtherAssets	76877000	USD
CY2019Q4	us-gaap	Assets Assets	8797150000	USD
CY2018Q4	us-gaap	Assets Assets	7952729000	USD
CY2019Q4	us-gaap	Liability For Claims And Claims Adjustment Expense Property Casualty Liability LiabilityForClaimsAndClaimsAdjustmentExpensePropertyCasualtyLiability	4067163000	USD
CY2018Q4	us-gaap	Liability For Claims And Claims Adjustment Expense Property Casualty Liability LiabilityForClaimsAndClaimsAdjustmentExpensePropertyCasualtyLiability	3893868000	USD
CY2019Q4	us-gaap	Unearned Premiums UnearnedPremiums	1523167000	USD
CY2018Q4	us-gaap	Unearned Premiums UnearnedPremiums	1431932000	USD
CY2019Q4	us-gaap	Long Term Debt LongTermDebt	550597000	USD
CY2018Q4	us-gaap	Long Term Debt LongTermDebt	439540000	USD
CY2019Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	2987000	USD
CY2018Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	1302000	USD
CY2019Q4	us-gaap	Accrued Salaries Current And Noncurrent AccruedSalariesCurrentAndNoncurrent	126753000	USD
CY2018Q4	us-gaap	Accrued Salaries Current And Noncurrent AccruedSalariesCurrentAndNoncurrent	116706000	USD
CY2019Q4	us-gaap	Other Liabilities OtherLiabilities	331547000	USD
CY2018Q4	us-gaap	Other Liabilities OtherLiabilities	277579000	USD
CY2019Q4	us-gaap	Liabilities Liabilities	6602214000	USD
CY2018Q4	us-gaap	Liabilities Liabilities	6160927000	USD
CY2019Q4	us-gaap	Preferred Stock Value PreferredStockValue	0	USD
CY2018Q4	us-gaap	Preferred Stock Value PreferredStockValue	0	USD
CY2019Q4	us-gaap	Common Stock Value CommonStockValue	206968000	USD
CY2018Q4	us-gaap	Common Stock Value CommonStockValue	205697000	USD
CY2019Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	418521000	USD
CY2018Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	390315000	USD
CY2019Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	2080529000	USD
CY2018Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	1858414000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	81750000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-77956000	USD
CY2019Q4	us-gaap	Treasury Stock Value TreasuryStockValue	592832000	USD
CY2018Q4	us-gaap	Treasury Stock Value TreasuryStockValue	584668000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	2194936000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	1791802000	USD
CY2019Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2018Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2018	us-gaap	Net Investment Income NetInvestmentIncome	195336000	USD
CY2017	us-gaap	Net Investment Income NetInvestmentIncome	161882000	USD
CY2019	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	2597171000	USD
CY2018	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	2436229000	USD
CY2017	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	2291027000	USD
CY2019	us-gaap	Net Investment Income NetInvestmentIncome	222543000	USD
CY2019	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	26715000	USD
CY2018	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	-18975000	USD
CY2017	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	11204000	USD
CY2019	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-8649000	USD
CY2018	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-29369000	USD
CY2017	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	0	USD
CY2019	us-gaap	Impairment Of Investments ImpairmentOfInvestments	3644000	USD
CY2018	us-gaap	Impairment Of Investments ImpairmentOfInvestments	6579000	USD
CY2017	us-gaap	Impairment Of Investments ImpairmentOfInvestments	4809000	USD
CY2019	us-gaap	Other Than Temporary Impairment Losses Investments Portion In Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	0	USD
CY2018	us-gaap	Other Than Temporary Impairment Losses Investments Portion In Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	0	USD
CY2017	us-gaap	Other Than Temporary Impairment Losses Investments Portion In Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	36000	USD
CY2019	us-gaap	Gain Loss On Investments GainLossOnInvestments	14422000	USD
CY2018	us-gaap	Gain Loss On Investments GainLossOnInvestments	-54923000	USD
CY2017	us-gaap	Gain Loss On Investments GainLossOnInvestments	6359000	USD
CY2019	us-gaap	Other Income OtherIncome	12355000	USD
CY2018	us-gaap	Other Income OtherIncome	9438000	USD
CY2017	us-gaap	Other Income OtherIncome	10716000	USD
CY2019	us-gaap	Revenues Revenues	2846491000	USD
CY2018	us-gaap	Revenues Revenues	2586080000	USD
CY2017	us-gaap	Revenues Revenues	2469984000	USD
CY2019	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	1551491000	USD
CY2018	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	1498134000	USD
CY2017	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	1345074000	USD
CY2019	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	535973000	USD
CY2018	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	495042000	USD
CY2017	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	469236000	USD
CY2019	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	358069000	USD
CY2018	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	331318000	USD
CY2017	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	333097000	USD
CY2019	us-gaap	Interest Expense Debt InterestExpenseDebt	33668000	USD
CY2018	us-gaap	Interest Expense Debt InterestExpenseDebt	24419000	USD
CY2017	us-gaap	Interest Expense Debt InterestExpenseDebt	24354000	USD
CY2019	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	30900000	USD
CY2018	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	25446000	USD
CY2017	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	36255000	USD
CY2019	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	2510101000	USD
CY2018	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	2374359000	USD
CY2017	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	2208016000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	336390000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	211721000	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	261968000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	60640000	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	35012000	USD
CY2017	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	62184000	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	4127000	USD
CY2018	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-2230000	USD
CY2017	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	30958000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	64767000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	32782000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	93142000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	271623000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	178939000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	168826000	USD
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.57
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.04
CY2017	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.89
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.53
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.00
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.84
CY2019	us-gaap	Net Income Loss NetIncomeLoss	271623000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	178939000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	168826000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	168021000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-97284000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	43015000	USD
CY2019	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome	0	USD
CY2018	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome	0	USD
CY2017	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome	23000	USD
CY2019	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	46000	USD
CY2018	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	-87000	USD
CY2017	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	116000	USD
CY2019	sigi	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Non Credit Other Than Temporary Impaired Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForNonCreditOtherThanTemporaryImpairedSecuritiesNetOfTax	0	USD
CY2018	sigi	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Non Credit Other Than Temporary Impaired Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForNonCreditOtherThanTemporaryImpairedSecuritiesNetOfTax	0	USD
CY2019Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	59461153	shares
CY2017	sigi	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Non Credit Other Than Temporary Impaired Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForNonCreditOtherThanTemporaryImpairedSecuritiesNetOfTax	-68000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	-530000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	-31316000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	4537000	USD
CY2019	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	-168505000	USD
CY2018	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	65881000	USD
CY2017	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	-38453000	USD
CY2019	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	-10898000	USD
CY2018	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	-8906000	USD
CY2017	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	-3700000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-2099000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-1680000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-1367000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	8799000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	7226000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	2333000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	159706000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-73107000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	36120000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	431329000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	105832000	USD
CY2017	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	204946000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	2194936000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	1791802000	USD
CY2017Q4	us-gaap	Stockholders Equity StockholdersEquity	1712957000	USD
CY2019	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.83
CY2018	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.74
CY2017	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.66
CY2018Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	58948554	shares
CY2017Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	58495122	shares
CY2016Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	57967199	shares
CY2019	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	22087	shares
CY2018	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	23493	shares
CY2017	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	28607	shares
CY2019	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	613678	shares
CY2018	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	540337	shares
CY2017	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	635521	shares
CY2019	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	123166	shares
CY2018	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	110398	shares
CY2017	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	136205	shares
CY2017	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	52100000	USD
CY2018Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	58948554	shares
CY2017Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	58495122	shares
CY2019	us-gaap	Net Income Loss NetIncomeLoss	271623000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	178939000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	168826000	USD
CY2019	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	55205000	USD
CY2018	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	44874000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	19077000	USD
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	14507000	USD
CY2017	us-gaap	Share Based Compensation ShareBasedCompensation	12089000	USD
CY2019	us-gaap	Income Loss From Equity Method Investments Net Of Dividends Or Distributions IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions	12773000	USD
CY2018	us-gaap	Income Loss From Equity Method Investments Net Of Dividends Or Distributions IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions	8341000	USD
CY2017	us-gaap	Income Loss From Equity Method Investments Net Of Dividends Or Distributions IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions	5362000	USD
CY2019	us-gaap	Equity Method Investment Dividends Or Distributions EquityMethodInvestmentDividendsOrDistributions	2807000	USD
CY2018	us-gaap	Equity Method Investment Dividends Or Distributions EquityMethodInvestmentDividendsOrDistributions	2924000	USD
CY2017	us-gaap	Equity Method Investment Dividends Or Distributions EquityMethodInvestmentDividendsOrDistributions	552000	USD
CY2019	us-gaap	Gain Loss On Investments GainLossOnInvestments	14422000	USD
CY2018	us-gaap	Gain Loss On Investments GainLossOnInvestments	-54923000	USD
CY2017	us-gaap	Gain Loss On Investments GainLossOnInvestments	6359000	USD
CY2019	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	-42000	USD
CY2018	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	-63000	USD
CY2017	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	-998000	USD
CY2019	sigi	Increase Decrease In Reserves For Losses And Loss Expenses Net Of Reinsurance Recoverables IncreaseDecreaseInReservesForLossesAndLossExpensesNetOfReinsuranceRecoverables	149232000	USD
CY2018	sigi	Increase Decrease In Reserves For Losses And Loss Expenses Net Of Reinsurance Recoverables IncreaseDecreaseInReservesForLossesAndLossExpensesNetOfReinsuranceRecoverables	168288000	USD
CY2017	sigi	Increase Decrease In Reserves For Losses And Loss Expenses Net Of Reinsurance Recoverables IncreaseDecreaseInReservesForLossesAndLossExpensesNetOfReinsuranceRecoverables	106226000	USD
CY2019	sigi	Increase Decrease In Unearned Premiums Net Of Prepaid Reinsurance IncreaseDecreaseInUnearnedPremiumsNetOfPrepaidReinsurance	82253000	USD
CY2018	sigi	Increase Decrease In Unearned Premiums Net Of Prepaid Reinsurance IncreaseDecreaseInUnearnedPremiumsNetOfPrepaidReinsurance	78058000	USD
CY2017	sigi	Increase Decrease In Unearned Premiums Net Of Prepaid Reinsurance IncreaseDecreaseInUnearnedPremiumsNetOfPrepaidReinsurance	79614000	USD
CY2019	us-gaap	Increase Decrease In Income Taxes IncreaseDecreaseInIncomeTaxes	7721000	USD
CY2018	us-gaap	Increase Decrease In Income Taxes IncreaseDecreaseInIncomeTaxes	2428000	USD
CY2017	us-gaap	Increase Decrease In Income Taxes IncreaseDecreaseInIncomeTaxes	30918000	USD
CY2019	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	53383000	USD
CY2018	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	23489000	USD
CY2017	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	65418000	USD
CY2019	sigi	Increase Decrease Deferred Policy Acquisition Costs IncreaseDecreaseDeferredPolicyAcquisitionCosts	-18574000	USD
CY2018	sigi	Increase Decrease Deferred Policy Acquisition Costs IncreaseDecreaseDeferredPolicyAcquisitionCosts	-17557000	USD
CY2017	sigi	Increase Decrease Deferred Policy Acquisition Costs IncreaseDecreaseDeferredPolicyAcquisitionCosts	-12491000	USD
CY2019	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	3226000	USD
CY2018	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	540000	USD
CY2017	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	1088000	USD
CY2019	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	-3748000	USD
CY2018	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	-26418000	USD
CY2017	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	-5714000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	39337000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	372000	USD
CY2017	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	2643000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	34998000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-13343000	USD
CY2017	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	27297000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	477495000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	454944000	USD
CY2017	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	379545000	USD
CY2019	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	0	USD
CY2018	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	7150000	USD
CY2017	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	0	USD
CY2019	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	1856125000	USD
CY2018	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	2918203000	USD
CY2017	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	2130362000	USD
CY2019	sigi	Paymentsto Acquire Equity Securities PaymentstoAcquireEquitySecurities	46397000	USD
CY2018	sigi	Paymentsto Acquire Equity Securities PaymentstoAcquireEquitySecurities	94344000	USD
CY2017	sigi	Paymentsto Acquire Equity Securities PaymentstoAcquireEquitySecurities	61931000	USD
CY2019	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	64908000	USD
CY2018	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	68578000	USD
CY2017	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	55830000	USD
CY2019	us-gaap	Payments To Acquire Short Term Investments PaymentsToAcquireShortTermInvestments	6087909000	USD
CY2018	us-gaap	Payments To Acquire Short Term Investments PaymentsToAcquireShortTermInvestments	4259734000	USD
CY2017	us-gaap	Payments To Acquire Short Term Investments PaymentsToAcquireShortTermInvestments	4280553000	USD
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	594743000	USD
CY2018	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	2030664000	USD
CY2017	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	1197920000	USD
CY2019	us-gaap	Proceeds From Sale Of Short Term Investments ProceedsFromSaleOfShortTermInvestments	6129885000	USD
CY2018	us-gaap	Proceeds From Sale Of Short Term Investments ProceedsFromSaleOfShortTermInvestments	4101530000	USD
CY2017	us-gaap	Proceeds From Sale Of Short Term Investments ProceedsFromSaleOfShortTermInvestments	4338318000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	16149000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	12106000	USD
CY2017	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	58832000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	626686000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	638916000	USD
CY2017	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	555216000	USD
CY2018	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-27791000	USD
CY2019	sigi	Proceedsfrom Saleof Equity Securities ProceedsfromSaleofEquitySecurities	137294000	USD
CY2018	sigi	Proceedsfrom Saleof Equity Securities ProceedsfromSaleofEquitySecurities	113339000	USD
CY2017	sigi	Proceedsfrom Saleof Equity Securities ProceedsfromSaleofEquitySecurities	37960000	USD
CY2019	us-gaap	Proceeds From Sale Of Equity Method Investments ProceedsFromSaleOfEquityMethodInvestments	17964000	USD
CY2018	us-gaap	Proceeds From Sale Of Equity Method Investments ProceedsFromSaleOfEquityMethodInvestments	3497000	USD
CY2017	us-gaap	Proceeds From Sale Of Equity Method Investments ProceedsFromSaleOfEquityMethodInvestments	0	USD
CY2019	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	19972000	USD
CY2018	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	28379000	USD
CY2017	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	21843000	USD
CY2019	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	9000	USD
CY2018	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	0	USD
CY2017	us-gaap	Proceeds From Sale Of Property Plant And Equipment ProceedsFromSaleOfPropertyPlantAndEquipment	0	USD
CY2019	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	30986000	USD
CY2018	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	16110000	USD
CY2017	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	14071000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-543623000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-435688000	USD
CY2017	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-332658000	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	47675000	USD
CY2018	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	42097000	USD
CY2017	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	37045000	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	8164000	USD
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	6556000	USD
CY2017	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	6015000	USD
CY2019	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	8243000	USD
CY2018	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	7252000	USD
CY2017	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	7599000	USD
CY2019	sigi	Borrowings From Subsidiaries BorrowingsFromSubsidiaries	355757000	USD
CY2018	sigi	Borrowings From Subsidiaries BorrowingsFromSubsidiaries	130000000	USD
CY2017	sigi	Borrowings From Subsidiaries BorrowingsFromSubsidiaries	84000000	USD
CY2019	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	250000000	USD
CY2018	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	130000000	USD
CY2017	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	84000000	USD
CY2019	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	977000	USD
CY2018	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	5646000	USD
CY2017	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	4121000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	57184000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-47047000	USD
CY2017	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-39582000	USD
CY2019	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-8944000	USD
CY2017	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	7305000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	16919000	USD
CY2019Q4	sigi	Unrealized Gain Loss On Investment Securities UnrealizedGainLossOnInvestmentSecurities	215688000	USD
CY2018Q4	sigi	Unrealized Gain Loss On Investment Securities UnrealizedGainLossOnInvestmentSecurities	2391000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	44710000	USD
CY2016Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	37405000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	7975000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	16919000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	44710000	USD
CY2019	us-gaap	Nature Of Operations NatureOfOperations	Organization<div style="line-height:120%;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Selective Insurance Group, Inc., through its subsidiaries, (collectively referred to as “we,” “us,” or “our”) offers standard commercial, standard personal, and excess and surplus ("E&S") lines property and casualty insurance products. Selective Insurance Group, Inc. (referred to as the “Parent”) was incorporated in New Jersey in 1977 and its corporate headquarters is located in Branchville, New Jersey. The Parent’s common stock is publicly traded on the NASDAQ Global Select Market under the symbol “SIGI.” We have provided a glossary of terms as Exhibit 99.1 to this Form 10-K, which defines certain industry-specific and other terms that are used in this Form 10-K.</span></div><div style="line-height:120%;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div><div style="line-height:120%;padding-bottom:13px;text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">We classify our business into four reportable segments, which are as follows:</span></div><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman; font-size:10pt;"><tr><td style="width:48px;"/><td/></tr><tr><td style="vertical-align:top"><div style="line-height:120%;font-size:10pt;padding-left:24px;"><span style="font-family:inherit;font-size:10pt;">•</span></div></td><td style="vertical-align:top;"><div style="line-height:120%;text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Standard Commercial Lines - comprised of insurance products and services provided in the standard marketplace to commercial enterprises, which are typically businesses, non-profit organizations, and local government agencies.</span></div></td></tr></table><div style="line-height:120%;text-align:left;padding-left:48px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman; font-size:10pt;"><tr><td style="width:48px;"/><td/></tr><tr><td style="vertical-align:top"><div style="line-height:120%;font-size:10pt;padding-left:24px;"><span style="font-family:inherit;font-size:10pt;">•</span></div></td><td style="vertical-align:top;"><div style="line-height:120%;text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Standard Personal Lines - comprised of insurance products and services, including flood insurance coverage, provided primarily to individuals acquiring coverage in the standard marketplace.</span></div></td></tr></table><div style="line-height:120%;text-align:left;padding-left:48px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman; font-size:10pt;"><tr><td style="width:48px;"/><td/></tr><tr><td style="vertical-align:top"><div style="line-height:120%;font-size:10pt;padding-left:24px;"><span style="font-family:inherit;font-size:10pt;">•</span></div></td><td style="vertical-align:top;"><div style="line-height:120%;text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">E&S Lines - comprised of insurance products and services provided to customers who have not obtained coverage in the standard marketplace.</span></div></td></tr></table><div style="line-height:120%;text-align:left;padding-left:48px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div><div style="line-height:120%;font-size:10pt;padding-left:24px;"><span style="font-family:inherit;font-size:10pt;">•</span></div><div style="line-height:120%;text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Investments - invests the premiums collected by our insurance operations, as well as amounts generated through our capital management strategies, which may include the issuance of debt and equity securities.</span></div>
CY2019	us-gaap	Use Of Estimates UseOfEstimates	Use of Estimates<div style="line-height:120%;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">The preparation of our Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported financial statement balances, as well as the disclosure of contingent assets and liabilities. Actual results could differ from those estimates.</span></div>
CY2019Q4	sigi	Percentof Portfolio Level3 Securities PercentofPortfolioLevel3Securities	0.01
CY2019	us-gaap	Depreciation Depreciation	18700000	USD
CY2018	us-gaap	Depreciation Depreciation	19500000	USD
CY2017	us-gaap	Depreciation Depreciation	17800000	USD
	sigi	Investment Yields Assumed In Premium Deficiency Assessment InvestmentYieldsAssumedInPremiumDeficiencyAssessment	0.035
	sigi	Investment Yields Assumed In Premium Deficiency Assessment InvestmentYieldsAssumedInPremiumDeficiencyAssessment	0.033
	sigi	Investment Yields Assumed In Premium Deficiency Assessment InvestmentYieldsAssumedInPremiumDeficiencyAssessment	0.029
CY2019	sigi	Interest Paid Operatingand Investing Activities InterestPaidOperatingandInvestingActivities	25089000	USD
CY2018	sigi	Interest Paid Operatingand Investing Activities InterestPaidOperatingandInvestingActivities	23992000	USD
CY2017	sigi	Interest Paid Operatingand Investing Activities InterestPaidOperatingandInvestingActivities	23905000	USD
CY2019	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	55825000	USD
CY2018	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	29193000	USD
CY2017	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	62000000	USD
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	8138000	USD
CY2018	us-gaap	Operating Lease Payments OperatingLeasePayments	0	USD
CY2017	us-gaap	Operating Lease Payments OperatingLeasePayments	0	USD
CY2019	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	16000	USD
CY2018	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	0	USD
CY2017	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	0	USD
CY2019	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	977000	USD
CY2018	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	5646000	USD
CY2017	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	4121000	USD
CY2019	us-gaap	Conversion Of Stock Amount Converted1 ConversionOfStockAmountConverted1	14250000	USD
CY2018	us-gaap	Conversion Of Stock Amount Converted1 ConversionOfStockAmountConverted1	944000	USD
CY2017	us-gaap	Conversion Of Stock Amount Converted1 ConversionOfStockAmountConverted1	4725000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	824000	USD
CY2018	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	4119000	USD
CY2017	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	278000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	13808000	USD
CY2018	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	0	USD
CY2017	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	0	USD
CY2019	us-gaap	Noncash Or Part Noncash Acquisition Fixed Assets Acquired1 NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1	89000	USD
CY2018	us-gaap	Noncash Or Part Noncash Acquisition Fixed Assets Acquired1 NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1	291000	USD
CY2017	us-gaap	Noncash Or Part Noncash Acquisition Fixed Assets Acquired1 NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1	0	USD
CY2019Q4	us-gaap	Cash Cash	300000	USD
CY2018Q4	us-gaap	Cash Cash	505000	USD
CY2019Q4	us-gaap	Restricted Cash RestrictedCash	7675000	USD
CY2018Q4	us-gaap	Restricted Cash RestrictedCash	16414000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	7975000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	16919000	USD
CY2017Q4	sigi	Unrealized Gain Loss On Investment Securities UnrealizedGainLossOnInvestmentSecurities	124679000	USD
CY2019Q4	sigi	Deferred Income Tax Expense Benefit On Investment Securities In Other Comprehensive Income DeferredIncomeTaxExpenseBenefitOnInvestmentSecuritiesInOtherComprehensiveIncome	45294000	USD
CY2018Q4	sigi	Deferred Income Tax Expense Benefit On Investment Securities In Other Comprehensive Income DeferredIncomeTaxExpenseBenefitOnInvestmentSecuritiesInOtherComprehensiveIncome	502000	USD
CY2017Q4	sigi	Deferred Income Tax Expense Benefit On Investment Securities In Other Comprehensive Income DeferredIncomeTaxExpenseBenefitOnInvestmentSecuritiesInOtherComprehensiveIncome	44103000	USD
CY2019Q4	sigi	Netunrealizedgainlossesoninvestmentsecuritiesinothercomprehensiveincomenetofdeferredincometax Netunrealizedgainlossesoninvestmentsecuritiesinothercomprehensiveincomenetofdeferredincometax	170394000	USD
CY2018Q4	sigi	Netunrealizedgainlossesoninvestmentsecuritiesinothercomprehensiveincomenetofdeferredincometax Netunrealizedgainlossesoninvestmentsecuritiesinothercomprehensiveincomenetofdeferredincometax	1889000	USD
CY2017Q4	sigi	Netunrealizedgainlossesoninvestmentsecuritiesinothercomprehensiveincomenetofdeferredincometax Netunrealizedgainlossesoninvestmentsecuritiesinothercomprehensiveincomenetofdeferredincometax	80576000	USD
CY2019	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	-168505000	USD
CY2018	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	65881000	USD
CY2017	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	-38453000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Amortized Cost Before Other Than Temporary Impairment HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment	20769000	USD
CY2019Q4	sigi	Held To Maturity Securities Net Unrealized Gains Losses HeldToMaturitySecuritiesNetUnrealizedGainsLosses	31000	USD
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	20800000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	1176000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	1000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	21975000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Amortized Cost Before Other Than Temporary Impairment HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment	37021000	USD
CY2018Q4	sigi	Held To Maturity Securities Net Unrealized Gains Losses HeldToMaturitySecuritiesNetUnrealizedGainsLosses	89000	USD
CY2018Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	37110000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	1359000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	152000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	38317000	USD
CY2019Q4	sigi	Percentage Decline In Fair Value Percentage PercentageDeclineInFairValuePercentage	0.01
CY2018Q4	sigi	Percentage Decline In Fair Value Percentage PercentageDeclineInFairValuePercentage	0.02
CY2019Q4	sigi	Unrealized Unrecognized Loss UnrealizedUnrecognizedLoss	100000	USD
CY2018Q4	sigi	Unrealized Unrecognized Loss UnrealizedUnrecognizedLoss	200000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	394027000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	1211000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	1229000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	3001602000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	13856000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	14820000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	2531172000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	5733000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	5926000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	168819000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	0	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	0	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	6095620000	USD
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	20800000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	21975000	USD
CY2019	sigi	Schedule Of Other Investment Portfolio By Strategy And Remaining Commitment Amount Associated With Each Strategy Textblock ScheduleOfOtherInvestmentPortfolioByStrategyAndRemainingCommitmentAmountAssociatedWithEachStrategyTextblock	<div style="line-height:120%;font-size:10pt;"><div style="padding-left:0px;text-indent:0px;line-height:normal;padding-top:10px;"><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman;font-size:10pt;width:100%;border-collapse:collapse;text-align:left;"><tr><td colspan="20"/></tr><tr><td style="width:22%;"/><td style="width:1%;"/><td style="width:1%;"/><td style="width:9%;"/><td style="width:1%;"/><td style="width:1%;"/><td style="width:11%;"/><td style="width:1%;"/><td style="width:1%;"/><td style="width:12%;"/><td style="width:1%;"/><td style="width:1%;"/><td style="width:10%;"/><td style="width:1%;"/><td style="width:1%;"/><td style="width:11%;"/><td style="width:1%;"/><td style="width:1%;"/><td style="width:12%;"/><td style="width:1%;"/></tr><tr><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:1px solid #000000;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">Other Investments</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:1px solid #000000;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="9" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;"><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">December 31, 2019</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:1px solid #000000;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="8" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;"><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">December 31, 2018</span></div></td></tr><tr><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">($ in thousands)</span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="3" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">Carrying</span></div><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">Value</span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">Remaining</span></div><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">Commitment</span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">Maximum</span></div><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">Exposure to Loss</span><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><sup style="vertical-align:top;line-height:120%;font-size:5pt">1</sup></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Carrying</span></div><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Value</span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Remaining<br/>Commitment</span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Maximum<br/>Exposure to Loss</span><span style="font-family:inherit;font-size:8pt;"><sup style="vertical-align:top;line-height:120%;font-size:5pt">1</sup></span></div></td></tr><tr><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">Alternative Investments</span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;padding-left:12px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Private equity</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">$</span></div></td><td style="vertical-align:bottom;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>118,352</span></span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>93,138</span></span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>211,490</span></span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>84,352</span></span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>93,688</span></span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>178,040</span></span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:12px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Private credit</span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>42,532</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>105,340</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>147,872</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>41,682</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>81,453</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>123,135</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;padding-left:12px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Real assets</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>23,256</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>20,741</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>43,997</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>27,862</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>27,129</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>54,991</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:20px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Total alternative investments</span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>184,140</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>219,219</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>403,359</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>153,896</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>202,270</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>356,166</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Other securities</span><span style="font-family:inherit;font-size:8pt;"><sup style="vertical-align:top;line-height:120%;font-size:5pt">2</sup></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>32,667</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>—</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>32,667</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>25,042</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>—</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>25,042</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Total other investments</span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;background-color:#ccffcc;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">$</span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;background-color:#ccffcc;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>216,807</span></span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>219,219</span></span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>436,026</span></span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>178,938</span></span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>202,270</span></span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>381,208</span></span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr></table></div><span style="font-family:inherit;font-size:10pt;"><br/></span></div>
CY2019Q4	sigi	Maximumexposuretocreditconcentrationriskofthe Companysstockholdersequityotherthancertain U.S.Governmentagencies MaximumexposuretocreditconcentrationriskoftheCompanysstockholdersequityotherthancertainU.S.governmentagencies	0.10
CY2018	sigi	Held To Maturity Securities Realized Gain HeldToMaturitySecuritiesRealizedGain	2000	USD
CY2019	us-gaap	Net Investment Income NetInvestmentIncome	222543000	USD
CY2018	us-gaap	Net Investment Income NetInvestmentIncome	195336000	USD
CY2017	us-gaap	Net Investment Income NetInvestmentIncome	161882000	USD
CY2019	us-gaap	Impairment Of Investments ImpairmentOfInvestments	3644000	USD
CY2019	us-gaap	Other Than Temporary Impairment Losses Investments Portion In Other Comprehensive Income Loss Before Tax Including Portion Attributable To Noncontrolling Interest OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossBeforeTaxIncludingPortionAttributableToNoncontrollingInterest	0	USD
CY2019	us-gaap	Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet	3644000	USD
CY2018	us-gaap	Impairment Of Investments ImpairmentOfInvestments	6579000	USD
CY2018	us-gaap	Other Than Temporary Impairment Losses Investments Portion In Other Comprehensive Income Loss Before Tax Including Portion Attributable To Noncontrolling Interest OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossBeforeTaxIncludingPortionAttributableToNoncontrollingInterest	0	USD
CY2018	us-gaap	Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet	6579000	USD
CY2017	us-gaap	Impairment Of Investments ImpairmentOfInvestments	4809000	USD
CY2017	us-gaap	Other Than Temporary Impairment Losses Investments Portion In Other Comprehensive Income Loss Before Tax Including Portion Attributable To Noncontrolling Interest OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossBeforeTaxIncludingPortionAttributableToNoncontrollingInterest	36000	USD
CY2017	us-gaap	Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet	4845000	USD
CY2019	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	26715000	USD
CY2018	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	-18975000	USD
CY2017	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	11204000	USD
CY2019	us-gaap	Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet	3644000	USD
CY2018	us-gaap	Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet	6579000	USD
CY2017	us-gaap	Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet	4845000	USD
CY2019	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	23071000	USD
CY2018	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	-25554000	USD
CY2017	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	6359000	USD
CY2019	sigi	Unrealized Gains Losseson Equity Securities UnrealizedGainsLossesonEquitySecurities	-8649000	USD
CY2018	sigi	Unrealized Gains Losseson Equity Securities UnrealizedGainsLossesonEquitySecurities	-29369000	USD
CY2017	sigi	Unrealized Gains Losseson Equity Securities UnrealizedGainsLossesonEquitySecurities	0	USD
CY2019	us-gaap	Gain Loss On Investments GainLossOnInvestments	14422000	USD
CY2018	us-gaap	Gain Loss On Investments GainLossOnInvestments	-54923000	USD
CY2017	us-gaap	Gain Loss On Investments GainLossOnInvestments	6359000	USD
CY2019	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	1219000	USD
CY2018	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	-3098000	USD
CY2019	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	-9868000	USD
CY2018	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	-26271000	USD
CY2019	sigi	Unrealized Gains Losseson Equity Securities UnrealizedGainsLossesonEquitySecurities	-8649000	USD
CY2018	sigi	Unrealized Gains Losseson Equity Securities UnrealizedGainsLossesonEquitySecurities	-29369000	USD
CY2019	sigi	Held To Maturity Securities Realized Gain HeldToMaturitySecuritiesRealizedGain	1000	USD
CY2017	sigi	Held To Maturity Securities Realized Gain HeldToMaturitySecuritiesRealizedGain	44000	USD
CY2019	sigi	Held To Maturity Securities Disposed Security Realized Loss HeldToMaturitySecuritiesDisposedSecurityRealizedLoss	15000	USD
CY2018	sigi	Held To Maturity Securities Disposed Security Realized Loss HeldToMaturitySecuritiesDisposedSecurityRealizedLoss	0	USD
CY2017	sigi	Held To Maturity Securities Disposed Security Realized Loss HeldToMaturitySecuritiesDisposedSecurityRealizedLoss	1000	USD
CY2019	us-gaap	Equity Securities Fv Ni Realized Gain EquitySecuritiesFvNiRealizedGain	24980000	USD
CY2018	us-gaap	Equity Securities Fv Ni Realized Gain EquitySecuritiesFvNiRealizedGain	23203000	USD
CY2017	us-gaap	Equity Securities Fv Ni Realized Gain EquitySecuritiesFvNiRealizedGain	5829000	USD
CY2019	us-gaap	Equity Securities Fv Ni Realized Loss EquitySecuritiesFvNiRealizedLoss	136000	USD
CY2018	us-gaap	Equity Securities Fv Ni Realized Loss EquitySecuritiesFvNiRealizedLoss	4508000	USD
CY2017	us-gaap	Equity Securities Fv Ni Realized Loss EquitySecuritiesFvNiRealizedLoss	1200000	USD
CY2019	sigi	Short Term Investments Realized Gains ShortTermInvestmentsRealizedGains	24000	USD
CY2018	sigi	Short Term Investments Realized Gains ShortTermInvestmentsRealizedGains	7000	USD
CY2017	sigi	Short Term Investments Realized Gains ShortTermInvestmentsRealizedGains	2000	USD
CY2019	sigi	Short Term Investments Realized Losses ShortTermInvestmentsRealizedLosses	-40000	USD
CY2018	sigi	Short Term Investments Realized Losses ShortTermInvestmentsRealizedLosses	-10000	USD
CY2017	sigi	Short Term Investments Realized Losses ShortTermInvestmentsRealizedLosses	-6000	USD
CY2019	sigi	Other Investments Realized Gains OtherInvestmentsRealizedGains	6000	USD
CY2018	sigi	Other Investments Realized Gains OtherInvestmentsRealizedGains	0	USD
CY2017	sigi	Other Investments Realized Gains OtherInvestmentsRealizedGains	494000	USD
CY2019	sigi	Other Investments Realized Losses OtherInvestmentsRealizedLosses	29000	USD
CY2018	sigi	Other Investments Realized Losses OtherInvestmentsRealizedLosses	2714000	USD
CY2017	sigi	Other Investments Realized Losses OtherInvestmentsRealizedLosses	859000	USD
CY2019	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	26715000	USD
CY2018	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	-18975000	USD
CY2017	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	11204000	USD
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	594700000	USD
CY2018	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	2030700000	USD
CY2017	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	1197900000	USD
CY2019	sigi	Proceedsfrom Saleof Equity Securities ProceedsfromSaleofEquitySecurities	137300000	USD
CY2018	sigi	Proceedsfrom Saleof Equity Securities ProceedsfromSaleofEquitySecurities	113300000	USD
CY2017	sigi	Proceedsfrom Saleof Equity Securities ProceedsfromSaleofEquitySecurities	38000000.0	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	336390000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	64767000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	271623000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	212683000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	44662000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	168021000	USD
CY2019	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Before Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax	58000	USD
CY2019	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax	12000	USD
CY2019	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	46000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-671000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	-141000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	-530000	USD
CY2019	sigi	Total Unrealized Gains Losses On Investment Securities Gross TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross	213296000	USD
CY2019	sigi	Total Unrealized Gains Losses On Investment Securities Tax TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax	44791000	USD
CY2019	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	-168505000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-13795000	USD
CY2019	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	-2897000	USD
CY2019	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	-10898000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-2657000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-558000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-2099000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	11138000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	2339000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	8799000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	202158000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	42452000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	159706000	USD
CY2019	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	538548000	USD
CY2019	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	107219000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	431329000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	211721000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	32782000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	178939000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-123145000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-25861000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-97284000	USD
CY2018	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Before Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax	-110000	USD
CY2018	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax	-23000	USD
CY2018	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	-87000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-39641000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	-8325000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	-31316000	USD
CY2018	sigi	Total Unrealized Gains Losses On Investment Securities Gross TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross	-83394000	USD
CY2018	sigi	Total Unrealized Gains Losses On Investment Securities Tax TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax	-17513000	USD
CY2018	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	65881000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-11273000	USD
CY2018	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	-2367000	USD
CY2018	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	-8906000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-2127000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-447000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-1680000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	9146000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	1920000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	7226000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-92540000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-19433000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-73107000	USD
CY2018	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	119181000	USD
CY2018	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	13349000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	105832000	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	261968000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	93142000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	168826000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	66894000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	23879000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	43015000	USD
CY2017	sigi	Non Credit Portion Of Other Than Temporary Impairment Losses Recognized In Other Comprehensive Income Gross NonCreditPortionOfOtherThanTemporaryImpairmentLossesRecognizedInOtherComprehensiveIncomeGross	36000	USD
CY2017	us-gaap	Other Than Temporary Impairment Losses Investments Portion In Other Comprehensive Income Loss Tax Portion Attributable To Parent OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossTaxPortionAttributableToParent	13000	USD
CY2017	us-gaap	Other Than Temporary Impairment Losses Investments Portion In Other Comprehensive Income Loss Net Of Tax Including Portion Attributable To Noncontrolling Interest Availableforsale Securities OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAvailableforsaleSecurities	23000	USD
CY2017	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Before Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax	179000	USD
CY2017	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax	63000	USD
CY2017	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	116000	USD
CY2017	sigi	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Non Credit Other Than Temporary Impaired Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForNonCreditOtherThanTemporaryImpairedSecuritiesBeforeTax	-104000	USD
CY2017	sigi	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Non Credit Other Than Temporary Impaired Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForNonCreditOtherThanTemporaryImpairedSecuritiesTax	-36000	USD
CY2017	sigi	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Non Credit Other Than Temporary Impaired Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForNonCreditOtherThanTemporaryImpairedSecuritiesNetOfTax	-68000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	6979000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	2442000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	4537000	USD
CY2017	sigi	Total Unrealized Gains Losses On Investment Securities Gross TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross	59876000	USD
CY2017	sigi	Total Unrealized Gains Losses On Investment Securities Tax TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax	21423000	USD
CY2017	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	-38453000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-4684000	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Gain Loss Included In Other Comprehensive Income Loss FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss	-379000	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Gain Loss Included In Earnings1 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1	245000	USD
CY2017	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	-984000	USD
CY2017	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	-3700000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-2102000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-735000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-1367000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	2582000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	249000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	2333000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	57294000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	21174000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	36120000	USD
CY2017	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	319262000	USD
CY2017	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	114316000	USD
CY2017	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	204946000	USD
CY2018	sigi	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Non Credit Other Than Temporary Impaired Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForNonCreditOtherThanTemporaryImpairedSecuritiesNetOfTax	0	USD
CY2018	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	-87000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	7226000	USD
CY2019	sigi	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Non Credit Other Than Temporary Impaired Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForNonCreditOtherThanTemporaryImpairedSecuritiesNetOfTax	0	USD
CY2019	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	46000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	8799000	USD
CY2017Q4	us-gaap	Cumulative Effect Of New Accounting Principle In Period Of Adoption CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	-25000000.0	USD
CY2019Q4	sigi	Net Asset Value NetAssetValue	37800000	USD
CY2018Q4	sigi	Net Asset Value NetAssetValue	37300000	USD
CY2018Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	7409000	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Transfers Out Of Level3 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3	30215000	USD
CY2019Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	34085000	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Purchases FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases	21282000	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Sales FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales	0	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Issues FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues	0	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Settlements FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements	-279000	USD
CY2019	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Transfers Into Level3 FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3	36022000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	21975000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	38317000	USD
CY2019	sigi	Terrorism Risk Insurance Program Companys Estimated Deductible TerrorismRiskInsuranceProgramCompanysEstimatedDeductible	359000000	USD
CY2019	sigi	Terrorism Risk Insurance Program Reimbursed Percentage Maximum TerrorismRiskInsuranceProgramReimbursedPercentageMaximum	0.80
CY2019	sigi	Terrorism Risk Insurance Program Annual Cap TerrorismRiskInsuranceProgramAnnualCap	100000000000	USD
CY2019Q4	sigi	Terrorism Risk Insurance Program Insurer Retainer TerrorismRiskInsuranceProgramInsurerRetainer	0.20
CY2019Q4	us-gaap	Reinsurance Recoverables ReinsuranceRecoverables	573235000	USD
CY2018Q4	us-gaap	Reinsurance Recoverables ReinsuranceRecoverables	549172000	USD
CY2019Q4	us-gaap	Prepaid Reinsurance Premiums PrepaidReinsurancePremiums	166705000	USD
CY2018Q4	us-gaap	Prepaid Reinsurance Premiums PrepaidReinsurancePremiums	157723000	USD
CY2019Q4	sigi	Remaining Reinsurance Balances RemainingReinsuranceBalances	739940000	USD
CY2018Q4	sigi	Remaining Reinsurance Balances RemainingReinsuranceBalances	706895000	USD
CY2019Q4	sigi	Collateral Of Reinsurance Recoverables CollateralOfReinsuranceRecoverables	110549000	USD
CY2018Q4	sigi	Collateral Of Reinsurance Recoverables CollateralOfReinsuranceRecoverables	112201000	USD
CY2019	us-gaap	Direct Premiums Written DirectPremiumsWritten	3084451000	USD
CY2018	us-gaap	Direct Premiums Written DirectPremiumsWritten	2890633000	USD
CY2017	us-gaap	Direct Premiums Written DirectPremiumsWritten	2733459000	USD
CY2019	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	24339000	USD
CY2018	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	26250000	USD
CY2017	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	26685000	USD
CY2019	us-gaap	Ceded Premiums Written CededPremiumsWritten	429366000	USD
CY2018	us-gaap	Ceded Premiums Written CededPremiumsWritten	402597000	USD
CY2017	us-gaap	Ceded Premiums Written CededPremiumsWritten	389503000	USD
CY2019	us-gaap	Premiums Written Net PremiumsWrittenNet	2679424000	USD
CY2018	us-gaap	Premiums Written Net PremiumsWrittenNet	2514286000	USD
CY2017	us-gaap	Premiums Written Net PremiumsWrittenNet	2370641000	USD
CY2019	us-gaap	Direct Premiums Earned DirectPremiumsEarned	2993157000	USD
CY2018	us-gaap	Direct Premiums Earned DirectPremiumsEarned	2808764000	USD
CY2018	us-gaap	Ceded Premiums Earned CededPremiumsEarned	398366000	USD
CY2017	us-gaap	Direct Premiums Earned DirectPremiumsEarned	2647488000	USD
CY2019	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	24399000	USD
CY2018	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	25831000	USD
CY2017	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	25831000	USD
CY2019	us-gaap	Ceded Premiums Earned CededPremiumsEarned	420385000	USD
CY2017	us-gaap	Ceded Premiums Earned CededPremiumsEarned	382292000	USD
CY2019	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	2597171000	USD
CY2018	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	2436229000	USD
CY2017	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	2291027000	USD
CY2019	us-gaap	Policyholder Benefits And Claims Incurred Gross PolicyholderBenefitsAndClaimsIncurredGross	1714880000	USD
CY2018	us-gaap	Policyholder Benefits And Claims Incurred Gross PolicyholderBenefitsAndClaimsIncurredGross	1706951000	USD
CY2017	us-gaap	Policyholder Benefits And Claims Incurred Gross PolicyholderBenefitsAndClaimsIncurredGross	1570678000	USD
CY2019	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Assumed ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed	22879000	USD
CY2018	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Assumed ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed	21469000	USD
CY2017	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Assumed ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed	17588000	USD
CY2019	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	186268000	USD
CY2018	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	230286000	USD
CY2017	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	243192000	USD
CY2019	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	1551491000	USD
CY2018	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	1498134000	USD
CY2017	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	1345074000	USD
CY2019	sigi	Percentage Of Unpaid Nfip Claims Ceded By Federal Government PercentageOfUnpaidNfipClaimsCededByFederalGovernment	1
CY2019	us-gaap	Schedule Of Liability For Unpaid Claims And Claims Adjustment Expense ScheduleOfLiabilityForUnpaidClaimsAndClaimsAdjustmentExpense	<div style="line-height:120%;padding-top:4px;font-size:10pt;"><div style="padding-left:0px;text-indent:0px;line-height:normal;padding-top:10px;"><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman;font-size:10pt;width:98.08429118773945%;border-collapse:collapse;text-align:left;"><tr><td colspan="11"/></tr><tr><td style="width:61%;"/><td style="width:1%;"/><td style="width:1%;"/><td style="width:10%;"/><td style="width:1%;"/><td style="width:1%;"/><td style="width:11%;"/><td style="width:1%;"/><td style="width:1%;"/><td style="width:11%;"/><td style="width:1%;"/></tr><tr><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:1px solid #000000;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">($ in thousands)</span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:1px solid #000000;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="3" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:1px solid #000000;"><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">2019</span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:1px solid #000000;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:1px solid #000000;"><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">2018</span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:1px solid #000000;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:1px solid #000000;"><div style="text-align:center;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">2017</span></div></td></tr><tr><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Gross reserves for loss and loss expense, at beginning of year</span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;background-color:#ccffcc;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">$</span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>3,893,868</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>3,771,240</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>3,691,719</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Less: reinsurance recoverable on unpaid loss and loss expense, at beginning of year</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>537,388</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>585,855</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>611,200</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Net reserves for loss and loss expense, at beginning of year</span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>3,356,480</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>3,185,385</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>3,080,519</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Incurred loss and loss expense for claims occurring in the:</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"> </span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:12px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Current year</span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>1,601,780</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>1,527,997</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>1,384,266</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;padding-left:12px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Prior years</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>(50,289</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-right:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">)</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>(29,863</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-right:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">)</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>(39,192</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-right:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">)</span></div></td></tr><tr><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Total incurred loss and loss expense</span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>1,551,491</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;border-top:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>1,498,134</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>1,345,074</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Paid loss and loss expense for claims occurring in the:</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"> </span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"> </span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:12px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Current year</span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>579,527</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>573,718</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>497,486</span></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;padding-left:12px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Prior years</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>805,443</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>753,321</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>742,722</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Total paid loss and loss expense</span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>1,384,970</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;border-top:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>1,327,039</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;border-top:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;padding-left:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>1,240,208</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#ccffcc;border-top:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Net reserves for loss and loss expense, at end of year</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>3,523,001</span></span></div></td><td style="vertical-align:bottom;border-top:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>3,356,480</span></span></div></td><td style="vertical-align:bottom;border-top:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>3,185,385</span></span></div></td><td style="vertical-align:bottom;border-top:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;background-color:#d0ffd0;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Add: Reinsurance recoverable on unpaid loss and loss expense, at end of year</span></div></td><td style="vertical-align:bottom;background-color:#d0ffd0;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#d0ffd0;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>544,162</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#d0ffd0;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#d0ffd0;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#d0ffd0;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>537,388</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#d0ffd0;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;background-color:#d0ffd0;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#d0ffd0;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>585,855</span></span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;background-color:#d0ffd0;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">Gross reserves for loss and loss expense at end of year</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">$</span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>4,067,163</span></span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>3,893,868</span></span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="overflow:hidden;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"> </span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>3,771,240</span></span></div></td><td style="vertical-align:bottom;border-bottom:3px double #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr></table></div><span style="font-family:inherit;font-size:10pt;"><br/></span></div><div style="line-height:120%;padding-top:4px;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><br/></span></div>
CY2018Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	3893868000	USD
CY2017Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	3771240000	USD
CY2016Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	3691719000	USD
CY2018Q4	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	537388000	USD
CY2017Q4	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	585855000	USD
CY2016Q4	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	611200000	USD
CY2018Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	3356480000	USD
CY2017Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	3185385000	USD
CY2016Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	3080519000	USD
CY2019	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	1601780000	USD
CY2018	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	1527997000	USD
CY2017	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	1384266000	USD
CY2019	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	-50289000	USD
CY2018	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	-29863000	USD
CY2017	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	-39192000	USD
CY2019	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	1551491000	USD
CY2018	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	1498134000	USD
CY2017	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	1345074000	USD
CY2019	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	579527000	USD
CY2018	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	573718000	USD
CY2017	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	497486000	USD
CY2019	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	805443000	USD
CY2018	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	753321000	USD
CY2017	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	742722000	USD
CY2019	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	1384970000	USD
CY2018	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	1327039000	USD
CY2017	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	1240208000	USD
CY2019Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	3523001000	USD
CY2018Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	3356480000	USD
CY2017Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	3185385000	USD
CY2019Q4	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	544162000	USD
CY2018Q4	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	537388000	USD
CY2017Q4	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	585855000	USD
CY2019Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	4067163000	USD
CY2018Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	3893868000	USD
CY2017Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	3771240000	USD
CY2019	us-gaap	Increase Decrease In Liability For Claims And Claims Adjustment Expense Reserve IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve	166500000	USD
CY2018	us-gaap	Increase Decrease In Liability For Claims And Claims Adjustment Expense Reserve IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve	171100000	USD
CY2017	us-gaap	Increase Decrease In Liability For Claims And Claims Adjustment Expense Reserve IncreaseDecreaseInLiabilityForClaimsAndClaimsAdjustmentExpenseReserve	104900000	USD
CY2019Q4	us-gaap	Salvage And Subrogation Recoveries Value SalvageAndSubrogationRecoveriesValue	76700000	USD
CY2018Q4	us-gaap	Salvage And Subrogation Recoveries Value SalvageAndSubrogationRecoveriesValue	67700000	USD
CY2017Q4	us-gaap	Salvage And Subrogation Recoveries Value SalvageAndSubrogationRecoveriesValue	64800000	USD
CY2019Q4	us-gaap	Shortduration Insurance Contracts Liability For Unpaid Claims And Allocated Claim Adjustment Expense Net ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndAllocatedClaimAdjustmentExpenseNet	3392713000	USD
CY2019Q4	us-gaap	Liability For Asbestos And Environmental Claims Gross LiabilityForAsbestosAndEnvironmentalClaimsGross	28700000	USD
CY2019Q4	us-gaap	Liability For Asbestos And Environmental Claims Net LiabilityForAsbestosAndEnvironmentalClaimsNet	21600000	USD
CY2018Q4	us-gaap	Liability For Asbestos And Environmental Claims Gross LiabilityForAsbestosAndEnvironmentalClaimsGross	30020000	USD
CY2018Q4	us-gaap	Liability For Asbestos And Environmental Claims Net LiabilityForAsbestosAndEnvironmentalClaimsNet	22783000	USD
CY2017Q4	us-gaap	Liability For Asbestos And Environmental Claims Gross LiabilityForAsbestosAndEnvironmentalClaimsGross	28415000	USD
CY2017Q4	us-gaap	Liability For Asbestos And Environmental Claims Net LiabilityForAsbestosAndEnvironmentalClaimsNet	21212000	USD
CY2016Q4	us-gaap	Liability For Asbestos And Environmental Claims Gross LiabilityForAsbestosAndEnvironmentalClaimsGross	29962000	USD
CY2016Q4	us-gaap	Liability For Asbestos And Environmental Claims Net LiabilityForAsbestosAndEnvironmentalClaimsNet	22716000	USD
CY2019	us-gaap	Liability For Asbestos And Environmental Claims Gross Incurred Loss1 LiabilityForAsbestosAndEnvironmentalClaimsGrossIncurredLoss1	348000	USD
CY2019	us-gaap	Liability For Asbestos And Environmental Claims Net Incurred Loss1 LiabilityForAsbestosAndEnvironmentalClaimsNetIncurredLoss1	-234000	USD
CY2018	us-gaap	Liability For Asbestos And Environmental Claims Gross Incurred Loss1 LiabilityForAsbestosAndEnvironmentalClaimsGrossIncurredLoss1	3059000	USD
CY2018	us-gaap	Liability For Asbestos And Environmental Claims Net Incurred Loss1 LiabilityForAsbestosAndEnvironmentalClaimsNetIncurredLoss1	-2877000	USD
CY2017	us-gaap	Liability For Asbestos And Environmental Claims Gross Incurred Loss1 LiabilityForAsbestosAndEnvironmentalClaimsGrossIncurredLoss1	126000	USD
CY2017	us-gaap	Liability For Asbestos And Environmental Claims Net Incurred Loss1 LiabilityForAsbestosAndEnvironmentalClaimsNetIncurredLoss1	0	USD
CY2019	us-gaap	Liability For Asbestos And Environmental Claims Gross Payment For Claims LiabilityForAsbestosAndEnvironmentalClaimsGrossPaymentForClaims	1667000	USD
CY2019	us-gaap	Liability For Asbestos And Environmental Claims Net Payment For Claims LiabilityForAsbestosAndEnvironmentalClaimsNetPaymentForClaims	1428000	USD
CY2018	us-gaap	Liability For Asbestos And Environmental Claims Gross Payment For Claims LiabilityForAsbestosAndEnvironmentalClaimsGrossPaymentForClaims	1454000	USD
CY2018	us-gaap	Liability For Asbestos And Environmental Claims Net Payment For Claims LiabilityForAsbestosAndEnvironmentalClaimsNetPaymentForClaims	1306000	USD
CY2017	us-gaap	Liability For Asbestos And Environmental Claims Gross Payment For Claims LiabilityForAsbestosAndEnvironmentalClaimsGrossPaymentForClaims	1673000	USD
CY2017	us-gaap	Liability For Asbestos And Environmental Claims Net Payment For Claims LiabilityForAsbestosAndEnvironmentalClaimsNetPaymentForClaims	1504000	USD
CY2019Q4	us-gaap	Liability For Asbestos And Environmental Claims Gross LiabilityForAsbestosAndEnvironmentalClaimsGross	28701000	USD
CY2019Q4	us-gaap	Liability For Asbestos And Environmental Claims Net LiabilityForAsbestosAndEnvironmentalClaimsNet	21589000	USD
CY2018Q4	us-gaap	Liability For Asbestos And Environmental Claims Gross LiabilityForAsbestosAndEnvironmentalClaimsGross	30020000	USD
CY2018Q4	us-gaap	Liability For Asbestos And Environmental Claims Net LiabilityForAsbestosAndEnvironmentalClaimsNet	22783000	USD
CY2017Q4	us-gaap	Liability For Asbestos And Environmental Claims Gross LiabilityForAsbestosAndEnvironmentalClaimsGross	28415000	USD
CY2017Q4	us-gaap	Liability For Asbestos And Environmental Claims Net LiabilityForAsbestosAndEnvironmentalClaimsNet	21212000	USD
CY2019Q4	us-gaap	Shortduration Insurance Contracts Incurred Claims And Allocated Claim Adjustment Expense Net ShortdurationInsuranceContractsIncurredClaimsAndAllocatedClaimAdjustmentExpenseNet	11547343000	USD
CY2019Q4	us-gaap	Shortduration Insurance Contracts Cumulative Paid Claims And Allocated Claim Adjustment Expense Net ShortdurationInsuranceContractsCumulativePaidClaimsAndAllocatedClaimAdjustmentExpenseNet	8514750000	USD
CY2019Q4	us-gaap	Shortduration Insurance Contracts Liability For Unpaid Claims And Allocated Claim Adjustment Expense Net ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndAllocatedClaimAdjustmentExpenseNet	3392713000	USD
CY2019Q4	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	544162000	USD
CY2019Q4	us-gaap	Shortduration Insurance Contracts Liability For Unpaid Claims And Claims Adjustment Expense Accumulated Unallocated Claim Adjustment Expense ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseAccumulatedUnallocatedClaimAdjustmentExpense	130288000	USD
CY2019Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	4067163000	USD
CY2019Q4	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	3687000	USD
CY2019Q4	us-gaap	Debt Instrument Unamortized Discount DebtInstrumentUnamortizedDiscount	6453000	USD
CY2019Q4	us-gaap	Long Term Debt LongTermDebt	550597000	USD
CY2018Q4	us-gaap	Long Term Debt LongTermDebt	439540000	USD
CY2019Q1	us-gaap	Deferred Finance Costs Gross DeferredFinanceCostsGross	3300000	USD
CY2019Q4	sigi	Federal Home Loan Bank Advances General Debt Obligations Disclosures Multiple Amount FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresMultipleAmount	20
CY2019Q4	sigi	Federal Home Loan Bank Advances General Debt Obligations Disclosures Multiple Amount FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresMultipleAmount	20
CY2019	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	4
CY2019	sigi	Geographic Concentration Of Net Premiums Written Percentage GeographicConcentrationOfNetPremiumsWrittenPercentage	0.19
CY2019	us-gaap	Net Investment Income NetInvestmentIncome	222543000	USD
CY2018	us-gaap	Net Investment Income NetInvestmentIncome	195336000	USD
CY2017	us-gaap	Net Investment Income NetInvestmentIncome	161882000	USD
CY2019	us-gaap	Gain Loss On Investments GainLossOnInvestments	14422000	USD
CY2018	us-gaap	Gain Loss On Investments GainLossOnInvestments	-54923000	USD
CY2017	us-gaap	Gain Loss On Investments GainLossOnInvestments	6359000	USD
CY2019	sigi	Total Investment Revenues TotalInvestmentRevenues	236965000	USD
CY2018	sigi	Total Investment Revenues TotalInvestmentRevenues	140413000	USD
CY2017	sigi	Total Investment Revenues TotalInvestmentRevenues	168241000	USD
CY2019	us-gaap	Revenues Revenues	2846491000	USD
CY2018	us-gaap	Revenues Revenues	2586080000	USD
CY2017	us-gaap	Revenues Revenues	2469984000	USD
CY2019	us-gaap	Net Investment Income NetInvestmentIncome	222543000	USD
CY2018	us-gaap	Net Investment Income NetInvestmentIncome	195336000	USD
CY2017	us-gaap	Net Investment Income NetInvestmentIncome	161882000	USD
CY2019	us-gaap	Gain Loss On Investments GainLossOnInvestments	14422000	USD
CY2018	us-gaap	Gain Loss On Investments GainLossOnInvestments	-54923000	USD
CY2017	us-gaap	Gain Loss On Investments GainLossOnInvestments	6359000	USD
CY2019	sigi	Total Investment Revenues TotalInvestmentRevenues	236965000	USD
CY2018	sigi	Total Investment Revenues TotalInvestmentRevenues	140413000	USD
CY2017	sigi	Total Investment Revenues TotalInvestmentRevenues	168241000	USD
CY2019	sigi	Taxoninvestmentincome Taxoninvestmentincome	45301000	USD
CY2018	sigi	Taxoninvestmentincome Taxoninvestmentincome	19560000	USD
CY2017	sigi	Taxoninvestmentincome Taxoninvestmentincome	45588000	USD
CY2019	sigi	Total Investment Income After Federal Income Tax TotalInvestmentIncomeAfterFederalIncomeTax	191664000	USD
CY2018	sigi	Total Investment Income After Federal Income Tax TotalInvestmentIncomeAfterFederalIncomeTax	120853000	USD
CY2017	sigi	Total Investment Income After Federal Income Tax TotalInvestmentIncomeAfterFederalIncomeTax	122653000	USD
CY2019	sigi	Total Investment Revenues TotalInvestmentRevenues	236965000	USD
CY2018	sigi	Total Investment Revenues TotalInvestmentRevenues	140413000	USD
CY2017	sigi	Total Investment Revenues TotalInvestmentRevenues	168241000	USD
CY2019	us-gaap	Interest Expense Debt InterestExpenseDebt	33668000	USD
CY2019	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	30900000	USD
CY2018	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	25446000	USD
CY2017	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	36255000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	336390000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	211721000	USD
CY2018	us-gaap	Interest Expense Debt InterestExpenseDebt	24419000	USD
CY2017	us-gaap	Interest Expense Debt InterestExpenseDebt	24354000	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	261968000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	271623000	USD
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	59421000	shares
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.57
CY2019	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	583000	shares
CY2019	us-gaap	Net Income Loss NetIncomeLoss	271623000	USD
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	60004000	shares
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.53
CY2018	us-gaap	Net Income Loss NetIncomeLoss	178939000	USD
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	58950000	shares
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.04
CY2018	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	763000	shares
CY2018	us-gaap	Net Income Loss NetIncomeLoss	178939000	USD
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	59713000	shares
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.00
CY2017	us-gaap	Net Income Loss NetIncomeLoss	168826000	USD
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	58458000	shares
CY2017	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.89
CY2017	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	899000	shares
CY2017	us-gaap	Net Income Loss NetIncomeLoss	168826000	USD
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	59357000	shares
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.84
CY2018	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.35
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2017	sigi	Decreasein Discounted Loss Reserve DecreaseinDiscountedLossReserve	35000000	USD
CY2017Q4	sigi	Provisional Increaseto Deferred Tax Asset ProvisionalIncreasetoDeferredTaxAsset	7500000	USD
CY2017Q4	sigi	Provisional Increaseto Deferred Tax Asset ProvisionalIncreasetoDeferredTaxAsset	7500000	USD
CY2018	sigi	Decreasein Discounted Loss Reserve DecreaseinDiscountedLossReserve	125000000	USD
CY2018Q4	sigi	Provisional Increaseto Deferred Tax Asset ProvisionalIncreasetoDeferredTaxAsset	26300000	USD
CY2017Q4	sigi	Provisional Increaseto Deferred Tax Asset ProvisionalIncreasetoDeferredTaxAsset	7500000	USD
CY2018Q4	sigi	Provisional Increaseto Deferred Tax Asset ProvisionalIncreasetoDeferredTaxAsset	26300000	USD
CY2018	sigi	Provisional Increaseto Deferred Tax Asset Per Year ProvisionalIncreasetoDeferredTaxAssetPerYear	3300000	USD
CY2019	sigi	Decreasein Discounted Loss Reserve DecreaseinDiscountedLossReserve	109500000	USD
CY2019Q4	sigi	Provisional Increaseto Deferred Tax Asset ProvisionalIncreasetoDeferredTaxAsset	23000000.0	USD
CY2018Q4	sigi	Provisional Increaseto Deferred Tax Asset ProvisionalIncreasetoDeferredTaxAsset	26300000	USD
CY2019Q4	sigi	Provisional Increaseto Deferred Tax Asset ProvisionalIncreasetoDeferredTaxAsset	23000000.0	USD
CY2019	sigi	Provisional Increaseto Deferred Tax Asset Per Year ProvisionalIncreasetoDeferredTaxAssetPerYear	2900000	USD
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	70642000	USD
CY2018	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	44461000	USD
CY2017	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	91689000	USD
CY2019	sigi	Income Tax Reconciliation Tax Advantaged Interest Income IncomeTaxReconciliationTaxAdvantagedInterestIncome	4909000	USD
CY2018	sigi	Income Tax Reconciliation Tax Advantaged Interest Income IncomeTaxReconciliationTaxAdvantagedInterestIncome	5518000	USD
CY2017	sigi	Income Tax Reconciliation Tax Advantaged Interest Income IncomeTaxReconciliationTaxAdvantagedInterestIncome	11510000	USD
CY2019	us-gaap	Income Tax Reconciliation Deductions Dividends IncomeTaxReconciliationDeductionsDividends	443000	USD
CY2018	us-gaap	Income Tax Reconciliation Deductions Dividends IncomeTaxReconciliationDeductionsDividends	647000	USD
CY2017	us-gaap	Income Tax Reconciliation Deductions Dividends IncomeTaxReconciliationDeductionsDividends	1961000	USD
CY2019	sigi	Federal Income Tax Expense Benefit Relatedto Executive Compensation FederalIncomeTaxExpenseBenefitRelatedtoExecutiveCompensation	-2985000	USD
CY2018	sigi	Federal Income Tax Expense Benefit Relatedto Executive Compensation FederalIncomeTaxExpenseBenefitRelatedtoExecutiveCompensation	-2279000	USD
CY2017	sigi	Federal Income Tax Expense Benefit Relatedto Executive Compensation FederalIncomeTaxExpenseBenefitRelatedtoExecutiveCompensation	0	USD
CY2019	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	3253000	USD
CY2018	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	3093000	USD
CY2017	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	4281000	USD
CY2019	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Deferred Tax Asset Income Tax Expense TaxCutsAndJobsActOf2017ChangeInTaxRateDeferredTaxAssetIncomeTaxExpense	0	USD
CY2018	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Deferred Tax Asset Income Tax Expense TaxCutsAndJobsActOf2017ChangeInTaxRateDeferredTaxAssetIncomeTaxExpense	0	USD
CY2017	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Deferred Tax Asset Income Tax Expense TaxCutsAndJobsActOf2017ChangeInTaxRateDeferredTaxAssetIncomeTaxExpense	20205000	USD
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-255000	USD
CY2018	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-4700000	USD
CY2017	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-1000000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	64767000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	32782000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	93142000	USD
CY2018	sigi	Capital Loss Carrybacks CapitalLossCarrybacks	3800000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Loss Reserves DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsLossReserves	48193000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Loss Reserves DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsLossReserves	43285000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Unearned Premiums Reserve DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsUnearnedPremiumsReserve	57004000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Unearned Premiums Reserve DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsUnearnedPremiumsReserve	53556000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	10646000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	8862000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	5727000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	9095000	USD
CY2019Q4	sigi	Deferred Tax Assets Unrealized Losses On Securities Gross DeferredTaxAssetsUnrealizedLossesOnSecuritiesGross	1059000	USD
CY2018Q4	sigi	Deferred Tax Assets Unrealized Losses On Securities Gross DeferredTaxAssetsUnrealizedLossesOnSecuritiesGross	1155000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	6478000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	5744000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	129107000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	121697000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Deferred Expense Deferred Policy Acquisition Cost DeferredTaxLiabilitiesDeferredExpenseDeferredPolicyAcquisitionCost	56949000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Deferred Expense Deferred Policy Acquisition Cost DeferredTaxLiabilitiesDeferredExpenseDeferredPolicyAcquisitionCost	53049000	USD
CY2019Q4	sigi	Deferred Tax Liabilities Investment Securities Unrealized Gain DeferredTaxLiabilitiesInvestmentSecuritiesUnrealizedGain	45294000	USD
CY2018Q4	sigi	Deferred Tax Liabilities Investment Securities Unrealized Gain DeferredTaxLiabilitiesInvestmentSecuritiesUnrealizedGain	502000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	7576000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	4904000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	12512000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	9702000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	122331000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	68157000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	6776000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	53540000	USD
CY2019	sigi	Changein Net Deferred Federal Income Tax Assets ChangeinNetDeferredFederalIncomeTaxAssets	46800000	USD
CY2019	us-gaap	Deferred Compensation Arrangement With Individual Contributions By Employer DeferredCompensationArrangementWithIndividualContributionsByEmployer	300000	USD
CY2018	us-gaap	Deferred Compensation Arrangement With Individual Contributions By Employer DeferredCompensationArrangementWithIndividualContributionsByEmployer	400000	USD
CY2017	us-gaap	Deferred Compensation Arrangement With Individual Contributions By Employer DeferredCompensationArrangementWithIndividualContributionsByEmployer	200000	USD
CY2019	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.0580
CY2019	sigi	Changein Defined Benefit Plan Discount Rate ChangeinDefinedBenefitPlanDiscountRate	113	USD
CY2019	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate	0.0295
CY2019Q4	us-gaap	Defined Benefit Plan Weighted Average Asset Allocations DefinedBenefitPlanWeightedAverageAssetAllocations	1
CY2019Q4	us-gaap	Defined Benefit Plan Weighted Average Asset Allocations DefinedBenefitPlanWeightedAverageAssetAllocations	1
CY2018Q4	us-gaap	Defined Benefit Plan Weighted Average Asset Allocations DefinedBenefitPlanWeightedAverageAssetAllocations	1
CY2019Q4	sigi	Percent Hedge Against Projected Benefit Obligation PercentHedgeAgainstProjectedBenefitObligation	0.57
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	126735	shares
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	14.37
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	0	shares
CY2019	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	0
CY2019	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	99912	shares
CY2019	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	13.74
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod	0	shares
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice	0
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	26823	shares
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	16.71
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P0Y3M29D
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	1300000	USD
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber	26823	shares
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice	16.71
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1	P0Y3M29D
CY2019Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1	1300000	USD
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	5200000	USD
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	4500000	USD
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	4000000.0	USD
CY2019	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	24500000	USD
CY2018	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	19300000	USD
CY2017	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	31200000	USD
CY2019	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	-8200000	USD
CY2018	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	-7000000.0	USD
CY2017	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	-15000000.0	USD
CY2019	us-gaap	Allocated Share Based Compensation Expense Net Of Tax AllocatedShareBasedCompensationExpenseNetOfTax	16300000	USD
CY2018	us-gaap	Allocated Share Based Compensation Expense Net Of Tax AllocatedShareBasedCompensationExpenseNetOfTax	12300000	USD
CY2017	us-gaap	Allocated Share Based Compensation Expense Net Of Tax AllocatedShareBasedCompensationExpenseNetOfTax	16200000	USD
CY2019	sigi	Related Party Transactions Contributions To Foundation RelatedPartyTransactionsContributionsToFoundation	1300000	USD
CY2018	sigi	Related Party Transactions Contributions To Foundation RelatedPartyTransactionsContributionsToFoundation	500000	USD
CY2019	us-gaap	Costs And Expenses Related Party CostsAndExpensesRelatedParty	2200000	USD
CY2017	us-gaap	Costs And Expenses Related Party CostsAndExpensesRelatedParty	2000000.0	USD
CY2019Q4	us-gaap	Due To Related Parties Current And Noncurrent DueToRelatedPartiesCurrentAndNoncurrent	1100000	USD
CY2018Q4	us-gaap	Due To Related Parties Current And Noncurrent DueToRelatedPartiesCurrentAndNoncurrent	1000000.0	USD
CY2019Q1	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	20700000	USD
CY2019Q1	us-gaap	Operating Lease Liability OperatingLeaseLiability	21000000.0	USD
CY2019Q1	us-gaap	Finance Lease Right Of Use Asset FinanceLeaseRightOfUseAsset	900000	USD
CY2019	us-gaap	Operating Lease Expense OperatingLeaseExpense	8808000	USD
CY2019	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	984000	USD
CY2019	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	16000	USD
CY2019	sigi	Finance Lease Expense FinanceLeaseExpense	1000000	USD
CY2019	us-gaap	Variable Lease Cost VariableLeaseCost	48000	USD
CY2019	us-gaap	Short Term Lease Cost ShortTermLeaseCost	2165000	USD
CY2019Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P6Y
CY2019Q4	us-gaap	Finance Lease Weighted Average Remaining Lease Term1 FinanceLeaseWeightedAverageRemainingLeaseTerm1	P2Y
CY2019Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.034
CY2019Q4	us-gaap	Finance Lease Weighted Average Discount Rate Percent FinanceLeaseWeightedAverageDiscountRatePercent	0.021
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	26535000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	27506000	USD
CY2019Q4	us-gaap	Finance Lease Right Of Use Asset FinanceLeaseRightOfUseAsset	731000	USD
CY2019Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	737000	USD
CY2019Q4	us-gaap	Finance Lease Liability Payments Due Next Twelve Months FinanceLeaseLiabilityPaymentsDueNextTwelveMonths	451000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	8244000	USD
CY2019Q4	sigi	Total Leases Due Next12 Months TotalLeasesDueNext12Months	8695000	USD
CY2019Q4	us-gaap	Finance Lease Liability Payments Due Year Two FinanceLeaseLiabilityPaymentsDueYearTwo	248000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	6168000	USD
CY2019Q4	sigi	Total Leases Due In Two Years TotalLeasesDueInTwoYears	6416000	USD
CY2019Q4	us-gaap	Finance Lease Liability Payments Due Year Three FinanceLeaseLiabilityPaymentsDueYearThree	54000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	4590000	USD
CY2019Q4	sigi	Total Leases Due In Five Years TotalLeasesDueInFiveYears	2920000	USD
CY2019Q4	us-gaap	Finance Lease Liability Payments Due After Year Five FinanceLeaseLiabilityPaymentsDueAfterYearFive	0	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	8638000	USD
CY2019Q4	sigi	Total Leases Due Thereafter TotalLeasesDueThereafter	8638000	USD
CY2019Q4	us-gaap	Finance Lease Liability Payments Due FinanceLeaseLiabilityPaymentsDue	753000	USD
CY2019Q4	sigi	Total Leases Due In Three Years TotalLeasesDueInThreeYears	4644000	USD
CY2019Q4	us-gaap	Finance Lease Liability Payments Due Year Four FinanceLeaseLiabilityPaymentsDueYearFour	0	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	3329000	USD
CY2019Q4	sigi	Total Leases Due In Four Years TotalLeasesDueInFourYears	3329000	USD
CY2019Q4	us-gaap	Finance Lease Liability Payments Due Year Five FinanceLeaseLiabilityPaymentsDueYearFive	0	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	2920000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	33889000	USD
CY2019Q4	sigi	Total Minimum Payment Required TotalMinimumPaymentRequired	34642000	USD
CY2019Q4	us-gaap	Finance Lease Liability Undiscounted Excess Amount FinanceLeaseLiabilityUndiscountedExcessAmount	16000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	2995000	USD
CY2019Q4	sigi	Totalimputedinterest Totalimputedinterest	3011000	USD
CY2019Q4	sigi	Finance Lease Liability Not Yet Commenced FinanceLeaseLiabilityNotYetCommenced	0	USD
CY2019Q4	sigi	Operating Lease Liability Not Yet Commenced OperatingLeaseLiabilityNotYetCommenced	3388000	USD
CY2019Q4	sigi	Totalleaseliabilitynotyetcommenced Totalleaseliabilitynotyetcommenced	3388000	USD
CY2019Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	737000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	27506000	USD
CY2019Q4	sigi	Totalleaseliability Totalleaseliability	28243000	USD
CY2018Q4	us-gaap	Capital Leases Future Minimum Payments Due Current CapitalLeasesFutureMinimumPaymentsDueCurrent	728000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due Current OperatingLeasesFutureMinimumPaymentsDueCurrent	7762000	USD
CY2018Q4	sigi	Total Leases Due Current Year TotalLeasesDueCurrentYear	8490000	USD
CY2018Q4	us-gaap	Capital Leases Future Minimum Payments Due In Two Years CapitalLeasesFutureMinimumPaymentsDueInTwoYears	141000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due In Two Years OperatingLeasesFutureMinimumPaymentsDueInTwoYears	7355000	USD
CY2018Q4	sigi	Totalleasesdueintwoyearspreleaseadoption Totalleasesdueintwoyearspreleaseadoption	7496000	USD
CY2018Q4	us-gaap	Capital Leases Future Minimum Payments Due In Three Years CapitalLeasesFutureMinimumPaymentsDueInThreeYears	22000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due In Three Years OperatingLeasesFutureMinimumPaymentsDueInThreeYears	5083000	USD
CY2018Q4	sigi	Totalleasesduethreeyears Totalleasesduethreeyears	5105000	USD
CY2018Q4	us-gaap	Capital Leases Future Minimum Payments Due In Four Years CapitalLeasesFutureMinimumPaymentsDueInFourYears	0	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due In Four Years OperatingLeasesFutureMinimumPaymentsDueInFourYears	3641000	USD
CY2018Q4	sigi	Totalleasesduefouryears Totalleasesduefouryears	3641000	USD
CY2018Q4	us-gaap	Capital Leases Future Minimum Payments Due In Five Years CapitalLeasesFutureMinimumPaymentsDueInFiveYears	0	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due In Five Years OperatingLeasesFutureMinimumPaymentsDueInFiveYears	2900000	USD
CY2018Q4	sigi	Totalleasesduefiveyears Totalleasesduefiveyears	2900000	USD
CY2018Q4	us-gaap	Capital Leases Future Minimum Payments Due Thereafter CapitalLeasesFutureMinimumPaymentsDueThereafter	0	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due Thereafter OperatingLeasesFutureMinimumPaymentsDueThereafter	9698000	USD
CY2018Q4	sigi	Totalleasesdueafter2023 Totalleasesdueafter2023	9698000	USD
CY2018Q4	us-gaap	Capital Leases Future Minimum Payments Due CapitalLeasesFutureMinimumPaymentsDue	891000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due OperatingLeasesFutureMinimumPaymentsDue	36439000	USD
CY2018Q4	sigi	Totalminimumpayment Totalminimumpayment	37330000	USD
CY2019Q4	sigi	Purchase Amount Of Annuities PurchaseAmountOfAnnuities	25500000	USD
CY2019Q4	sigi	Statutory Accounting Practices Statutory Unassigned Surplus StatutoryAccountingPracticesStatutoryUnassignedSurplus	1396800000	USD
CY2018Q4	sigi	Statutory Accounting Practices Statutory Unassigned Surplus StatutoryAccountingPracticesStatutoryUnassignedSurplus	1232800000	USD
CY2019Q4	us-gaap	Statutory Accounting Practices Statutory Capital And Surplus Balance StatutoryAccountingPracticesStatutoryCapitalAndSurplusBalance	1932400000	USD
CY2018Q4	us-gaap	Statutory Accounting Practices Statutory Capital And Surplus Balance StatutoryAccountingPracticesStatutoryCapitalAndSurplusBalance	1768400000	USD
CY2019	us-gaap	Statutory Accounting Practices Statutory Net Income Amount StatutoryAccountingPracticesStatutoryNetIncomeAmount	292700000	USD
CY2018	us-gaap	Statutory Accounting Practices Statutory Net Income Amount StatutoryAccountingPracticesStatutoryNetIncomeAmount	210600000	USD
CY2017	us-gaap	Statutory Accounting Practices Statutory Net Income Amount StatutoryAccountingPracticesStatutoryNetIncomeAmount	221200000	USD
CY2019Q4	us-gaap	Statutory Accounting Practices Statutory Amount Available For Dividend Payments With Regulatory Approval StatutoryAccountingPracticesStatutoryAmountAvailableForDividendPaymentsWithRegulatoryApproval	266700000	USD
CY2019	sigi	Maximum Borrowing Percentage MaximumBorrowingPercentage	0.10
CY2019Q4	sigi	New Jersey Dividend Restriction NewJerseyDividendRestriction	0.10
CY2019Q4	sigi	New York Dividend Restriction NewYorkDividendRestriction	0.10
CY2019Q4	sigi	Dividend Restriction New York DividendRestrictionNewYork	1
CY2019	us-gaap	Cash Dividends Paid To Parent Company CashDividendsPaidToParentCompany	110000000.0	USD
CY2019Q4	us-gaap	Statutory Accounting Practices Statutory Amount Available For Dividend Payments With Regulatory Approval StatutoryAccountingPracticesStatutoryAmountAvailableForDividendPaymentsWithRegulatoryApproval	266700000	USD
CY2019Q1	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	632573000	USD
CY2018Q1	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	591828000	USD
CY2019Q2	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	642619000	USD
CY2018Q2	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	604836000	USD
CY2019Q3	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	653620000	USD
CY2018Q3	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	614277000	USD
CY2019Q4	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	668359000	USD
CY2018Q4	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	625288000	USD
CY2019Q1	us-gaap	Net Investment Income NetInvestmentIncome	50618000	USD
CY2018Q1	us-gaap	Net Investment Income NetInvestmentIncome	43231000	USD
CY2019Q2	us-gaap	Net Investment Income NetInvestmentIncome	58505000	USD
CY2018Q2	us-gaap	Net Investment Income NetInvestmentIncome	45553000	USD
CY2019Q3	us-gaap	Net Investment Income NetInvestmentIncome	55826000	USD
CY2018Q3	us-gaap	Net Investment Income NetInvestmentIncome	52443000	USD
CY2019Q4	us-gaap	Net Investment Income NetInvestmentIncome	57594000	USD
CY2018Q4	us-gaap	Net Investment Income NetInvestmentIncome	54109000	USD
CY2019Q1	us-gaap	Gain Loss On Investments GainLossOnInvestments	13451000	USD
CY2018Q1	us-gaap	Gain Loss On Investments GainLossOnInvestments	-10549000	USD
CY2019Q2	us-gaap	Gain Loss On Investments GainLossOnInvestments	4027000	USD
CY2018Q2	us-gaap	Gain Loss On Investments GainLossOnInvestments	-1652000	USD
CY2019Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	-2183000	USD
CY2018Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	-4787000	USD
CY2019Q4	us-gaap	Gain Loss On Investments GainLossOnInvestments	-873000	USD
CY2018Q4	us-gaap	Gain Loss On Investments GainLossOnInvestments	-37935000	USD
CY2019Q1	us-gaap	Other Income OtherIncome	2320000	USD
CY2018Q1	us-gaap	Other Income OtherIncome	2179000	USD
CY2019Q2	us-gaap	Other Income OtherIncome	3053000	USD
CY2018Q2	us-gaap	Other Income OtherIncome	3179000	USD
CY2019Q3	us-gaap	Other Income OtherIncome	3162000	USD
CY2018Q3	us-gaap	Other Income OtherIncome	2538000	USD
CY2019Q4	us-gaap	Other Income OtherIncome	3820000	USD
CY2018Q4	us-gaap	Other Income OtherIncome	1542000	USD
CY2019Q1	us-gaap	Revenues Revenues	698962000	USD
CY2018Q1	us-gaap	Revenues Revenues	626689000	USD
CY2019Q2	us-gaap	Revenues Revenues	708204000	USD
CY2018Q2	us-gaap	Revenues Revenues	651916000	USD
CY2019	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	24399000	USD
CY2019	us-gaap	Ceded Premiums Earned CededPremiumsEarned	420385000	USD
CY2019	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	2597171000	USD
CY2019	us-gaap	Premiums Percentage Assumed To Net PremiumsPercentageAssumedToNet	0.01
CY2019Q3	us-gaap	Revenues Revenues	710425000	USD
CY2018Q3	us-gaap	Revenues Revenues	664471000	USD
CY2019Q4	us-gaap	Revenues Revenues	728900000	USD
CY2018Q4	us-gaap	Revenues Revenues	643004000	USD
CY2019Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	73694000	USD
CY2018Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	19931000	USD
CY2019Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	90225000	USD
CY2018Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	72525000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	71178000	USD
CY2018Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	67130000	USD
CY2019Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	101293000	USD
CY2018Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	52135000	USD
CY2019Q1	us-gaap	Net Income Loss NetIncomeLoss	61348000	USD
CY2018Q1	us-gaap	Net Income Loss NetIncomeLoss	18925000	USD
CY2019Q2	us-gaap	Net Income Loss NetIncomeLoss	72266000	USD
CY2018Q2	us-gaap	Net Income Loss NetIncomeLoss	58819000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	56150000	USD
CY2018Q3	us-gaap	Net Income Loss NetIncomeLoss	55435000	USD
CY2019Q4	us-gaap	Net Income Loss NetIncomeLoss	81859000	USD
CY2018Q4	us-gaap	Net Income Loss NetIncomeLoss	45760000	USD
CY2019Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.04
CY2018Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.32
CY2019Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.22
CY2018Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.00
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.94
CY2018Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.94
CY2019Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.38
CY2018Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.77
CY2019Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.02
CY2018Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.32
CY2019Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.21
CY2018Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.99
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.93
CY2018Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.93
CY2019Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.36
CY2018Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.76
CY2019Q4	us-gaap	Summary Of Investments Other Than Investments In Related Parties Cost SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost	6472113000	USD
CY2019Q4	us-gaap	Summary Of Investments Other Than Investments In Related Parties Carrying Amount SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount	6688654000	USD
CY2018	us-gaap	Direct Premiums Earned DirectPremiumsEarned	2808764000	USD
CY2018	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	25831000	USD
CY2018	us-gaap	Ceded Premiums Earned CededPremiumsEarned	398366000	USD
CY2018	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	2436229000	USD
CY2018	us-gaap	Premiums Percentage Assumed To Net PremiumsPercentageAssumedToNet	0.01
CY2017	us-gaap	Direct Premiums Earned DirectPremiumsEarned	2647488000	USD
CY2017	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	25831000	USD
CY2017	us-gaap	Ceded Premiums Earned CededPremiumsEarned	382292000	USD
CY2017	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	2291027000	USD
CY2017	us-gaap	Premiums Percentage Assumed To Net PremiumsPercentageAssumedToNet	0.01
CY2018Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	13900000	USD
CY2017Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	14600000	USD
CY2016Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	11480000	USD
CY2019	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	2730000	USD
CY2018	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	4022000	USD
CY2017	us-gaap	Valuation Allowances And Reserves Charged To Cost And Expense ValuationAllowancesAndReservesChargedToCostAndExpense	6414000	USD
CY2019	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	5830000	USD
CY2018	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	4722000	USD
CY2017	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	3294000	USD
CY2019Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	10800000	USD
CY2018Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	13900000	USD
CY2017Q4	us-gaap	Valuation Allowances And Reserves Balance ValuationAllowancesAndReservesBalance	14600000	USD
CY2019Q4	us-gaap	Supplementary Insurance Information Deferred Policy Acquisition Costs SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts	271186000	USD
CY2019Q4	us-gaap	Supplementary Insurance Information Liability For Future Policy Benefits Losses Claims And Loss Expense Reserves SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves	4067163000	USD
CY2019Q4	us-gaap	Supplementary Insurance Information Unearned Premiums SupplementaryInsuranceInformationUnearnedPremiums	1523167000	USD
CY2019	us-gaap	Supplementary Insurance Information Premium Revenue SupplementaryInsuranceInformationPremiumRevenue	2597171000	USD
CY2019	us-gaap	Supplementary Insurance Information Net Investment Income SupplementaryInsuranceInformationNetInvestmentIncome	236965000	USD
CY2019	us-gaap	Supplementary Insurance Information Benefits Claims Losses And Settlement Expense SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense	1551491000	USD
CY2019	us-gaap	Supplementary Insurance Information Amortization Of Deferred Policy Acquisition Costs SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts	535973000	USD
CY2019	us-gaap	Supplementary Insurance Information Other Operating Expense SupplementaryInsuranceInformationOtherOperatingExpense	345714000	USD
CY2019	us-gaap	Supplementary Insurance Information Premiums Written SupplementaryInsuranceInformationPremiumsWritten	2679424000	USD
CY2019	us-gaap	Supplementary Insurance Information Other Operating Expense SupplementaryInsuranceInformationOtherOperatingExpense	345714000	USD
CY2019	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	358069000	USD
CY2019	us-gaap	Supplementary Insurance Information Other Operating Expense SupplementaryInsuranceInformationOtherOperatingExpense	345714000	USD
CY2018Q4	us-gaap	Supplementary Insurance Information Deferred Policy Acquisition Costs SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts	252612000	USD
CY2018Q4	us-gaap	Supplementary Insurance Information Liability For Future Policy Benefits Losses Claims And Loss Expense Reserves SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves	3893868000	USD
CY2018Q4	us-gaap	Supplementary Insurance Information Unearned Premiums SupplementaryInsuranceInformationUnearnedPremiums	1431932000	USD
CY2018	us-gaap	Supplementary Insurance Information Premium Revenue SupplementaryInsuranceInformationPremiumRevenue	2436229000	USD
CY2018	us-gaap	Supplementary Insurance Information Net Investment Income SupplementaryInsuranceInformationNetInvestmentIncome	140413000	USD
CY2018	us-gaap	Supplementary Insurance Information Benefits Claims Losses And Settlement Expense SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense	1498134000	USD
CY2018	us-gaap	Supplementary Insurance Information Amortization Of Deferred Policy Acquisition Costs SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts	495042000	USD
CY2018	us-gaap	Supplementary Insurance Information Other Operating Expense SupplementaryInsuranceInformationOtherOperatingExpense	321880000	USD
CY2018	us-gaap	Supplementary Insurance Information Premiums Written SupplementaryInsuranceInformationPremiumsWritten	2514286000	USD
CY2018	us-gaap	Supplementary Insurance Information Other Operating Expense SupplementaryInsuranceInformationOtherOperatingExpense	321880000	USD
CY2018	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	331318000	USD
CY2018	us-gaap	Supplementary Insurance Information Other Operating Expense SupplementaryInsuranceInformationOtherOperatingExpense	321880000	USD
CY2017Q4	us-gaap	Supplementary Insurance Information Deferred Policy Acquisition Costs SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts	235055000	USD
CY2017Q4	us-gaap	Supplementary Insurance Information Liability For Future Policy Benefits Losses Claims And Loss Expense Reserves SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves	3771240000	USD
CY2017Q4	us-gaap	Supplementary Insurance Information Unearned Premiums SupplementaryInsuranceInformationUnearnedPremiums	1349644000	USD
CY2017	us-gaap	Supplementary Insurance Information Premium Revenue SupplementaryInsuranceInformationPremiumRevenue	2291027000	USD
CY2017	us-gaap	Supplementary Insurance Information Net Investment Income SupplementaryInsuranceInformationNetInvestmentIncome	168241000	USD
CY2017	us-gaap	Supplementary Insurance Information Benefits Claims Losses And Settlement Expense SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense	1345074000	USD
CY2017	us-gaap	Supplementary Insurance Information Amortization Of Deferred Policy Acquisition Costs SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts	469236000	USD
CY2017	us-gaap	Supplementary Insurance Information Other Operating Expense SupplementaryInsuranceInformationOtherOperatingExpense	322381000	USD
CY2017	us-gaap	Supplementary Insurance Information Premiums Written SupplementaryInsuranceInformationPremiumsWritten	2370641000	USD
CY2017	us-gaap	Supplementary Insurance Information Other Operating Expense SupplementaryInsuranceInformationOtherOperatingExpense	322381000	USD
CY2017	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	333097000	USD
CY2017	us-gaap	Supplementary Insurance Information Other Operating Expense SupplementaryInsuranceInformationOtherOperatingExpense	322381000	USD
CY2019	us-gaap	Direct Premiums Earned DirectPremiumsEarned	2993157000	USD

Files In Submission

Name	View Source	Status
0000230557-20-000005-index-headers.html	Edgar Link	pending
0000230557-20-000005-index.html	Edgar Link	pending
0000230557-20-000005.txt	Edgar Link	pending
0000230557-20-000005-xbrl.zip	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
item5charta01.jpg	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
R1.htm	Edgar Link	pending
R10.htm	Edgar Link	pending
R100.htm	Edgar Link	pending
R101.htm	Edgar Link	pending
R102.htm	Edgar Link	pending
R103.htm	Edgar Link	pending
R104.htm	Edgar Link	pending
R105.htm	Edgar Link	pending
R106.htm	Edgar Link	pending
R107.htm	Edgar Link	pending
R108.htm	Edgar Link	pending
R109.htm	Edgar Link	pending
R11.htm	Edgar Link	pending
R110.htm	Edgar Link	pending
R111.htm	Edgar Link	pending
R112.htm	Edgar Link	pending
R113.htm	Edgar Link	pending
R114.htm	Edgar Link	pending
R115.htm	Edgar Link	pending
R116.htm	Edgar Link	pending
R117.htm	Edgar Link	pending
R118.htm	Edgar Link	pending
R119.htm	Edgar Link	pending
R12.htm	Edgar Link	pending
R120.htm	Edgar Link	pending
R121.htm	Edgar Link	pending
R122.htm	Edgar Link	pending
R123.htm	Edgar Link	pending
R124.htm	Edgar Link	pending
R125.htm	Edgar Link	pending
R126.htm	Edgar Link	pending
R127.htm	Edgar Link	pending
R128.htm	Edgar Link	pending
R129.htm	Edgar Link	pending
R13.htm	Edgar Link	pending
R130.htm	Edgar Link	pending
R131.htm	Edgar Link	pending
R132.htm	Edgar Link	pending
R133.htm	Edgar Link	pending
R14.htm	Edgar Link	pending
R15.htm	Edgar Link	pending
R16.htm	Edgar Link	pending
R17.htm	Edgar Link	pending
R18.htm	Edgar Link	pending
R19.htm	Edgar Link	pending
R2.htm	Edgar Link	pending
R20.htm	Edgar Link	pending
R21.htm	Edgar Link	pending
R22.htm	Edgar Link	pending
R23.htm	Edgar Link	pending
R24.htm	Edgar Link	pending
R25.htm	Edgar Link	pending
R26.htm	Edgar Link	pending
R27.htm	Edgar Link	pending
R28.htm	Edgar Link	pending
R29.htm	Edgar Link	pending
R3.htm	Edgar Link	pending
R30.htm	Edgar Link	pending
R31.htm	Edgar Link	pending
R32.htm	Edgar Link	pending
R33.htm	Edgar Link	pending
R34.htm	Edgar Link	pending
R35.htm	Edgar Link	pending
R36.htm	Edgar Link	pending
R37.htm	Edgar Link	pending
R38.htm	Edgar Link	pending
R39.htm	Edgar Link	pending
R4.htm	Edgar Link	pending
R40.htm	Edgar Link	pending
R41.htm	Edgar Link	pending
R42.htm	Edgar Link	pending
R43.htm	Edgar Link	pending
R44.htm	Edgar Link	pending
R45.htm	Edgar Link	pending
R46.htm	Edgar Link	pending
R47.htm	Edgar Link	pending
R48.htm	Edgar Link	pending
R49.htm	Edgar Link	pending
R5.htm	Edgar Link	pending
R50.htm	Edgar Link	pending
R51.htm	Edgar Link	pending
R52.htm	Edgar Link	pending
R53.htm	Edgar Link	pending
R54.htm	Edgar Link	pending
R55.htm	Edgar Link	pending
R56.htm	Edgar Link	pending
R57.htm	Edgar Link	pending
R58.htm	Edgar Link	pending
R59.htm	Edgar Link	pending
R6.htm	Edgar Link	pending
R60.htm	Edgar Link	pending
R61.htm	Edgar Link	pending
R62.htm	Edgar Link	pending
R63.htm	Edgar Link	pending
R64.htm	Edgar Link	pending
R65.htm	Edgar Link	pending
R66.htm	Edgar Link	pending
R67.htm	Edgar Link	pending
R68.htm	Edgar Link	pending
R69.htm	Edgar Link	pending
R7.htm	Edgar Link	pending
R70.htm	Edgar Link	pending
R71.htm	Edgar Link	pending
R72.htm	Edgar Link	pending
R73.htm	Edgar Link	pending
R74.htm	Edgar Link	pending
R75.htm	Edgar Link	pending
R76.htm	Edgar Link	pending
R77.htm	Edgar Link	pending
R78.htm	Edgar Link	pending
R79.htm	Edgar Link	pending
R8.htm	Edgar Link	pending
R80.htm	Edgar Link	pending
R81.htm	Edgar Link	pending
R82.htm	Edgar Link	pending
R83.htm	Edgar Link	pending
R84.htm	Edgar Link	pending
R85.htm	Edgar Link	pending
R86.htm	Edgar Link	pending
R87.htm	Edgar Link	pending
R88.htm	Edgar Link	pending
R89.htm	Edgar Link	pending
R9.htm	Edgar Link	pending
R90.htm	Edgar Link	pending
R91.htm	Edgar Link	pending
R92.htm	Edgar Link	pending
R93.htm	Edgar Link	pending
R94.htm	Edgar Link	pending
R95.htm	Edgar Link	pending
R96.htm	Edgar Link	pending
R97.htm	Edgar Link	pending
R98.htm	Edgar Link	pending
R99.htm	Edgar Link	pending
report.css	Edgar Link	pending
Show.js	Edgar Link	pending
sigi-12312019x10k.htm	Edgar Link	pending
sigi-12312019x10k_htm.xml	Edgar Link	completed
sigi-20191231.xsd	Edgar Link	pending
sigi-20191231_cal.xml	Edgar Link	unprocessable
sigi-20191231_def.xml	Edgar Link	unprocessable
sigi-20191231_lab.xml	Edgar Link	unprocessable
sigi-20191231_pre.xml	Edgar Link	unprocessable
sigi-ex103212312019xq4.htm	Edgar Link	pending
sigi-ex103412312019xq4.htm	Edgar Link	pending
sigi-ex2112312019xq4.htm	Edgar Link	pending
sigi-ex23112312019xq4.htm	Edgar Link	pending
sigi-ex2410poa12312019.htm	Edgar Link	pending
sigi-ex2411poa12312019.htm	Edgar Link	pending
sigi-ex2412poa12312019.htm	Edgar Link	pending
sigi-ex2413poa12312019.htm	Edgar Link	pending
sigi-ex241poa12312019x.htm	Edgar Link	pending
sigi-ex242poa12312019x.htm	Edgar Link	pending
sigi-ex243poa12312019x.htm	Edgar Link	pending
sigi-ex244poa12312019x.htm	Edgar Link	pending
sigi-ex245poa12312019x.htm	Edgar Link	pending
sigi-ex246poa12312019x.htm	Edgar Link	pending
sigi-ex247poa12312019x.htm	Edgar Link	pending
sigi-ex248poa12312019x.htm	Edgar Link	pending
sigi-ex249poa12312019x.htm	Edgar Link	pending
sigi-ex31112312019xq4.htm	Edgar Link	pending
sigi-ex31212312019xq4.htm	Edgar Link	pending
sigi-ex32112312019xq4.htm	Edgar Link	pending
sigi-ex32212312019xq4.htm	Edgar Link	pending
sigi-ex4812312019xq4.htm	Edgar Link	pending
sigi-ex99112312019xq4.htm	Edgar Link	pending

Create your account

Find Stocks Worth Researching

Deeply Understand Businesses

Value Businesses Intelligently

$SIGI
Selective Insurance Group Inc Stock $sigi

2020 Q1 Form 10-K Financial Statement

#000023055720000005 Filed on February 12, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$SIGI Selective Insurance Group Inc Stock $sigi

2020 Q1 Form 10-K Financial Statement

#000023055720000005 Filed on February 12, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$SIGI
Selective Insurance Group Inc Stock $sigi