$SIGI
Selective Insurance Group Inc Stock $sigi

$sigi Overview Financials Valuation SEC Filings Company Website

2019 Q3 Form 10-Q Financial Statement

#000023055719000023 Filed on August 01, 2019

Income Statement

Concept	2019 Q3	2019 Q2	2018 Q2
Revenue	$710.4M	$708.2M	$651.9M
YoY Change	6.92%	8.63%	6.09%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin	$8.600M	$12.10M	$3.300M
YoY Change	14.67%	266.67%
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$136.6M	$133.4M	$122.7M
YoY Change	9.69%	8.76%	5.22%
% of Gross Profit
Operating Expenses	$631.8M	$610.6M	$573.3M
YoY Change	6.85%	6.51%	4.33%
Operating Profit
YoY Change
Interest Expense	-$7.400M	-$7.400M	-$6.100M
YoY Change	21.31%	21.31%	0.0%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$71.18M	$90.23M	$72.53M
YoY Change	6.03%	24.41%	23.07%
Income Tax	$15.03M	$17.96M	$13.71M
% Of Pretax Income	21.11%	19.9%	18.9%
Net Earnings	$56.15M	$72.27M	$58.82M
YoY Change	1.29%	22.86%	41.99%
Net Earnings / Revenue	7.9%	10.2%	9.02%
Basic Earnings Per Share	$0.94	$1.22	$1.00
Diluted Earnings Per Share	$0.93	$1.21	$0.99
COMMON SHARES
Basic Shares Outstanding	59.37M shares	59.23M shares	58.75M shares
Diluted Shares Outstanding

Balance Sheet

Concept	2019 Q3	2019 Q2	2018 Q2
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$10.16M	$7.643M	$16.48M
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	$76.42M	$73.68M	$62.73M
YoY Change	18.99%	17.45%	-5.32%
Goodwill	$7.849M	$7.849M	$7.849M
YoY Change	0.0%	0.0%	0.0%
Intangibles
YoY Change
Long-Term Investments	$6.552B	$6.421B	$5.666B
YoY Change	11.78%	13.34%	2.95%
Other Assets	$15.20M	$21.80M	$63.20M
YoY Change	-76.51%	-65.51%	4.64%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$8.719B	$8.576B	$7.706B
YoY Change	9.17%	11.29%	2.36%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$129.7M	$117.9M	$85.40M
YoY Change	35.95%	38.06%	-17.25%
Deferred Revenue
YoY Change
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$132.4M	$121.1M	$90.50M
YoY Change	23.16%	33.81%	-14.06%
LONG-TERM LIABILITIES
Long-Term Debt	$550.7M	$550.8M	$439.3M
YoY Change	25.33%	25.38%	0.09%
Other Long-Term Liabilities	$273.2M	$280.2M	$236.5M
YoY Change	-6.57%	18.48%	-4.71%
Total Long-Term Liabilities	$823.9M	$831.0M	$675.8M
YoY Change	12.59%	22.97%	-1.64%
TOTAL LIABILITIES
Total Short-Term Liabilities	$132.4M	$121.1M	$90.50M
Total Long-Term Liabilities	$823.9M	$831.0M	$675.8M
Total Liabilities	$6.582B	$6.516B	$6.008B
YoY Change	5.34%	8.47%	2.24%
SHAREHOLDERS EQUITY
Retained Earnings	$2.012B	$1.968B	$1.780B
YoY Change	10.3%	10.59%	8.41%
Common Stock	$619.2M	$614.0M	$587.1M
YoY Change	4.77%	4.59%	4.04%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$592.7M	$591.4M	$584.4M
YoY Change	1.4%	1.2%	1.09%
Treasury Stock Shares	44.02M shares	44.00M shares	43.89M shares
Shareholders Equity	$2.137B	$2.060B	$1.698B
YoY Change
Total Liabilities & Shareholders Equity	$8.719B	$8.576B	$7.706B
YoY Change	9.17%	11.29%	2.36%

Cashflow Statement

Concept	2019 Q3	2019 Q2	2018 Q2
OPERATING ACTIVITIES
Net Income	$56.15M	$72.27M	$58.82M
YoY Change	1.29%	22.86%	41.99%
Depreciation, Depletion And Amortization	$136.6M	$133.4M	$122.7M
YoY Change	9.69%	8.76%	5.22%
Cash From Operating Activities	$151.1M	$118.5M	$100.0M
YoY Change	-24.53%	18.5%	40.85%
INVESTING ACTIVITIES
Capital Expenditures	-$7.400M	-$9.000M	-$4.600M
YoY Change	64.44%	95.65%	119.05%
Acquisitions
YoY Change
Other Investing Activities	-$128.6M	-$103.2M	-$32.40M
YoY Change	-31.05%	218.52%	-45.08%
Cash From Investing Activities	-$136.0M	-$112.3M	-$36.90M
YoY Change	-28.8%	204.34%	-39.61%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-12.60M	-9.100M	-63.50M
YoY Change	-2.33%	-85.67%	693.75%
NET CHANGE
Cash From Operating Activities	151.1M	118.5M	100.0M
Cash From Investing Activities	-136.0M	-112.3M	-36.90M
Cash From Financing Activities	-12.60M	-9.100M	-63.50M
Net Change In Cash	2.500M	-2.900M	-400.0K
YoY Change	-167.57%	625.0%	-121.05%
FREE CASH FLOW
Cash From Operating Activities	$151.1M	$118.5M	$100.0M
Capital Expenditures	-$7.400M	-$9.000M	-$4.600M
Free Cash Flow	$158.5M	$127.5M	$104.6M
YoY Change	-22.57%	21.89%	43.09%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
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CY2019Q2	us-gaap	Equity Securities Fv Ni Cost EquitySecuritiesFvNiCost	135761000	USD
CY2019Q1	us-gaap	Finance Lease Liability FinanceLeaseLiability	900000	USD
	dei	Amendment Flag AmendmentFlag	false
	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	Q2
	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2019
	dei	Entity Central Index Key EntityCentralIndexKey	0000230557
	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
	dei	Entity Small Business EntitySmallBusiness	false
CY2018Q4	sigi	Htm Securities Percentof Invested Assets HTMSecuritiesPercentofInvestedAssets	0.01
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	dei	Entity File Number EntityFileNumber	001-33067
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	dei	Document Type DocumentType	10-Q
	dei	Document Quarterly Report DocumentQuarterlyReport	true
	dei	Document Period End Date DocumentPeriodEndDate	2019-06-30
	dei	Document Transition Report DocumentTransitionReport	false
	dei	Entity Registrant Name EntityRegistrantName	SELECTIVE INSURANCE GROUP, INC
	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	NJ
	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	22-2168890
	dei	Entity Address Address Line1 EntityAddressAddressLine1	40 Wantage Avenue
	dei	Entity Address City Or Town EntityAddressCityOrTown	Branchville,
	dei	Entity Address State Or Province EntityAddressStateOrProvince	NJ
	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	07890
	dei	City Area Code CityAreaCode	973
	dei	Local Phone Number LocalPhoneNumber	948-3000
	dei	Security12b Title Security12bTitle	Common Stock, par value $2 per share
	dei	Trading Symbol TradingSymbol	SIGI
	dei	Security Exchange Name SecurityExchangeName	NASDAQ
	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
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CY2018Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	72525000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	163919000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	92456000	USD
CY2019Q2	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	17958000	USD
CY2018Q2	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	12782000	USD
	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	30539000	USD
	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	13215000	USD
CY2019Q2	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	1000	USD
CY2018Q2	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	924000	USD
	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-234000	USD
	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	1497000	USD
CY2019Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	17959000	USD
CY2018Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	13706000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	30305000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14712000	USD
CY2019Q2	us-gaap	Net Income Loss NetIncomeLoss	72266000	USD
CY2018Q2	us-gaap	Net Income Loss NetIncomeLoss	58819000	USD
	us-gaap	Net Income Loss NetIncomeLoss	133614000	USD
	us-gaap	Net Income Loss NetIncomeLoss	77744000	USD
CY2019Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.22
CY2018Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.00
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.25
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.32
CY2019Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.21
CY2018Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.99
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.23
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.30
CY2019Q2	us-gaap	Net Income Loss NetIncomeLoss	72266000	USD
CY2018Q2	us-gaap	Net Income Loss NetIncomeLoss	58819000	USD
	us-gaap	Net Income Loss NetIncomeLoss	133614000	USD
	us-gaap	Net Income Loss NetIncomeLoss	77744000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	66002000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-18955000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	147315000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-86353000	USD
CY2019Q2	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	17000	USD
CY2018Q2	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	6000	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	24000	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	16000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	1027000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	-2267000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	1878000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	-5861000	USD
CY2019Q2	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	-64958000	USD
CY2018Q2	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	16694000	USD
	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	-145413000	USD
	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	80508000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-524000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-420000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-1049000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-840000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-524000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-420000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-1049000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	65482000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-16274000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	146462000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-79668000	USD
CY2019Q2	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	137748000	USD
CY2018Q2	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	42545000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	280076000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-1924000	USD
CY2019Q2	us-gaap	Stockholders Equity StockholdersEquity	2059544000	USD
CY2018Q2	us-gaap	Stockholders Equity StockholdersEquity	1698155000	USD
CY2019Q2	us-gaap	Stockholders Equity StockholdersEquity	2059544000	USD
CY2018Q2	us-gaap	Stockholders Equity StockholdersEquity	1698155000	USD
CY2019Q2	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.20
CY2018Q2	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.18
	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.40
	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.36
CY2019Q1	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	59222905	shares
CY2018Q1	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	58747505	shares
CY2018Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	58948554	shares
CY2017Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	58495122	shares
CY2019Q2	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	5218	shares
CY2018Q2	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	6075	shares
	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	10912	shares
	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	12373	shares
CY2019Q2	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	101650	shares
CY2018Q2	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	83754	shares
	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	473278	shares
	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	433009	shares
CY2019Q2	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	1665	shares
CY2018Q2	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	2282	shares
	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	104636	shares
	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	105452	shares
CY2019Q2	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	59328108	shares
CY2018Q2	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	58835052	shares
CY2019Q2	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	59328108	shares
CY2018Q2	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	58835052	shares
	us-gaap	Net Income Loss NetIncomeLoss	133614000	USD
	us-gaap	Net Income Loss NetIncomeLoss	77744000	USD
	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	28327000	USD
	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	21771000	USD
	us-gaap	Share Based Compensation ShareBasedCompensation	11654000	USD
	us-gaap	Share Based Compensation ShareBasedCompensation	9636000	USD
	us-gaap	Income Loss From Equity Method Investments Net Of Dividends Or Distributions IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions	4934000	USD
	us-gaap	Income Loss From Equity Method Investments Net Of Dividends Or Distributions IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions	1628000	USD
	us-gaap	Equity Method Investment Dividends Or Distributions EquityMethodInvestmentDividendsOrDistributions	2157000	USD
	us-gaap	Equity Method Investment Dividends Or Distributions EquityMethodInvestmentDividendsOrDistributions	1450000	USD
	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	0	USD
	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	-29000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	17478000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	-12201000	USD
	sigi	Increase Decrease In Reserves For Losses And Loss Expenses Net Of Reinsurance Recoverables IncreaseDecreaseInReservesForLossesAndLossExpensesNetOfReinsuranceRecoverables	105082000	USD
	sigi	Increase Decrease In Reserves For Losses And Loss Expenses Net Of Reinsurance Recoverables IncreaseDecreaseInReservesForLossesAndLossExpensesNetOfReinsuranceRecoverables	82978000	USD
	sigi	Increase Decrease In Unearned Premiums Net Of Prepaid Reinsurance IncreaseDecreaseInUnearnedPremiumsNetOfPrepaidReinsurance	99152000	USD
	sigi	Increase Decrease In Unearned Premiums Net Of Prepaid Reinsurance IncreaseDecreaseInUnearnedPremiumsNetOfPrepaidReinsurance	83143000	USD
	us-gaap	Increase Decrease In Income Taxes IncreaseDecreaseInIncomeTaxes	1698000	USD
	us-gaap	Increase Decrease In Income Taxes IncreaseDecreaseInIncomeTaxes	9887000	USD
	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	107190000	USD
	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	74144000	USD
	us-gaap	Deferred Policy Acquisition Costs Period Increase Decrease DeferredPolicyAcquisitionCostsPeriodIncreaseDecrease	20516000	USD
	us-gaap	Deferred Policy Acquisition Costs Period Increase Decrease DeferredPolicyAcquisitionCostsPeriodIncreaseDecrease	13412000	USD
	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	1399000	USD
	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	-2000	USD
	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	-29124000	USD
	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	-46478000	USD
	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	22320000	USD
	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	6550000	USD
	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-13583000	USD
	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-64372000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities Continuing Operations NetCashProvidedByUsedInOperatingActivitiesContinuingOperations	165140000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities Continuing Operations NetCashProvidedByUsedInOperatingActivitiesContinuingOperations	92257000	USD
	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	0	USD
	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	3650000	USD
	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	891241000	USD
	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	1331607000	USD
	sigi	Paymentsto Acquire Equity Securities PaymentstoAcquireEquitySecurities	24699000	USD
	sigi	Paymentsto Acquire Equity Securities PaymentstoAcquireEquitySecurities	46402000	USD
	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	25822000	USD
	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	26032000	USD
	us-gaap	Payments To Acquire Short Term Investments PaymentsToAcquireShortTermInvestments	3258852000	USD
	us-gaap	Payments To Acquire Short Term Investments PaymentsToAcquireShortTermInvestments	1462238000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	372159000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	938276000	USD
	us-gaap	Proceeds From Sale Of Short Term Investments ProceedsFromSaleOfShortTermInvestments	3291878000	USD
	us-gaap	Proceeds From Sale Of Short Term Investments ProceedsFromSaleOfShortTermInvestments	1463726000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	4643000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	3654000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	236705000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	311590000	USD
	sigi	Proceedsfrom Saleof Equity Securities ProceedsfromSaleofEquitySecurities	30094000	USD
	sigi	Proceedsfrom Saleof Equity Securities ProceedsfromSaleofEquitySecurities	43590000	USD
	us-gaap	Proceeds From Sale Of Other Investments ProceedsFromSaleOfOtherInvestments	12609000	USD
	us-gaap	Proceeds From Sale Of Other Investments ProceedsFromSaleOfOtherInvestments	3497000	USD
	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	14489000	USD
	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	15927000	USD
	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	16985000	USD
	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	6733000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities Continuing Operations NetCashProvidedByUsedInInvestingActivitiesContinuingOperations	-255022000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities Continuing Operations NetCashProvidedByUsedInInvestingActivitiesContinuingOperations	-96402000	USD
	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	22940000	USD
	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	20437000	USD
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	6715000	USD
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	6245000	USD
	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	5100000	USD
	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	3930000	USD
	us-gaap	Proceeds From Debt Net Of Issuance Costs ProceedsFromDebtNetOfIssuanceCosts	340757000	USD
	us-gaap	Proceeds From Debt Net Of Issuance Costs ProceedsFromDebtNetOfIssuanceCosts	130000000	USD
	us-gaap	Repayments Of Debt RepaymentsOfDebt	235000000	USD
	us-gaap	Repayments Of Debt RepaymentsOfDebt	130000000	USD
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	596000	USD
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	1333000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities Continuing Operations NetCashProvidedByUsedInFinancingActivitiesContinuingOperations	80606000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities Continuing Operations NetCashProvidedByUsedInFinancingActivitiesContinuingOperations	-24085000	USD
	sigi	Cashand Restricted Cash Period Increase Decrease CashandRestrictedCashPeriodIncreaseDecrease	-9276000	USD
	sigi	Cashand Restricted Cash Period Increase Decrease CashandRestrictedCashPeriodIncreaseDecrease	-28230000	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
CY2019Q2	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	7643000	USD
CY2018Q2	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	16480000	USD
	us-gaap	Interest Paid InterestPaid	10512000	USD
	us-gaap	Interest Paid InterestPaid	12064000	USD
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	28000000	USD
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	4193000	USD
	us-gaap	Operating Lease Payments OperatingLeasePayments	3994000	USD
	us-gaap	Operating Lease Payments OperatingLeasePayments	0	USD
	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	7000	USD
	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	0	USD
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	596000	USD
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	1333000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	814000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	0	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	12881000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	0	USD
	us-gaap	Noncash Or Part Noncash Acquisition Fixed Assets Acquired1 NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1	0	USD
	us-gaap	Noncash Or Part Noncash Acquisition Fixed Assets Acquired1 NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1	18000	USD
CY2019Q2	us-gaap	Cash Cash	504000	USD
CY2018Q4	us-gaap	Cash Cash	505000	USD
CY2019Q2	us-gaap	Restricted Cash RestrictedCash	7139000	USD
CY2018Q4	us-gaap	Restricted Cash RestrictedCash	16414000	USD
CY2019Q2	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	7643000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	16919000	USD
CY2019Q2	sigi	Htm Securities Percentof Invested Assets HTMSecuritiesPercentofInvestedAssets	0.01
CY2019Q2	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	32400000	USD
CY2019Q2	sigi	Net Unrealized Unrecognized Gains Losseson Heldto Maturity Securities NetUnrealizedUnrecognizedGainsLossesonHeldtoMaturitySecurities	1600000	USD
CY2018Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	37100000	USD
CY2018Q4	sigi	Net Unrealized Unrecognized Gains Losseson Heldto Maturity Securities NetUnrealizedUnrecognizedGainsLossesonHeldtoMaturitySecurities	1300000	USD
CY2019Q2	sigi	Unrealized Unrecognized Loss UnrealizedUnrecognizedLoss	100000	USD
CY2018Q4	sigi	Unrealized Unrecognized Loss UnrealizedUnrecognizedLoss	200000	USD
CY2019Q2	us-gaap	Available For Sale Securities Amortized Cost AvailableForSaleSecuritiesAmortizedCost	5571491000	USD
CY2019Q2	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	195287000	USD
CY2019Q2	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	8880000	USD
CY2019Q2	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	5757898000	USD
CY2018Q4	us-gaap	Available For Sale Securities Amortized Cost AvailableForSaleSecuritiesAmortizedCost	5270798000	USD
CY2018Q4	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	47369000	USD
CY2018Q4	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	45067000	USD
CY2018Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	5273100000	USD
CY2019Q2	sigi	Percent Of Securities In An Unrealized Unrecognized Loss Position PercentOfSecuritiesInAnUnrealizedUnrecognizedLossPosition	0.01
CY2018Q4	sigi	Percent Of Securities In An Unrealized Unrecognized Loss Position PercentOfSecuritiesInAnUnrealizedUnrecognizedLossPosition	0.02
CY2019Q2	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	280140000	USD
CY2019Q2	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	9480000	USD
CY2019Q2	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	9526000	USD
CY2019Q2	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	2237395000	USD
CY2019Q2	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	16860000	USD
CY2019Q2	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	18109000	USD
CY2019Q2	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	3065577000	USD
CY2019Q2	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	6024000	USD
CY2019Q2	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	6220000	USD
CY2019Q2	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	174786000	USD
CY2019Q2	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	0	USD
CY2019Q2	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	0	USD
CY2019Q2	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	5757898000	USD
CY2019Q2	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	32364000	USD
CY2019Q2	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	33855000	USD
CY2019Q2	us-gaap	Assets Held By Insurance Regulators AssetsHeldByInsuranceRegulators	27000000.0	USD
CY2019Q2	us-gaap	Security Owned And Pledged As Collateral Fair Value SecurityOwnedAndPledgedAsCollateralFairValue	197700000	USD
CY2019Q2	sigi	Maximumexposuretocreditconcentrationriskofthe Companysstockholdersequityotherthancertain U.S.Governmentagencies MaximumexposuretocreditconcentrationriskoftheCompanysstockholdersequityotherthancertainU.S.governmentagencies	0.10
CY2019Q2	us-gaap	Net Investment Income NetInvestmentIncome	58505000	USD
CY2018Q2	us-gaap	Net Investment Income NetInvestmentIncome	45553000	USD
	us-gaap	Net Investment Income NetInvestmentIncome	109123000	USD
	us-gaap	Net Investment Income NetInvestmentIncome	88784000	USD
CY2019Q2	us-gaap	Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet	1000000.0	USD
CY2018Q2	us-gaap	Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet	2800000	USD
	us-gaap	Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet	1100000	USD
	us-gaap	Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet	4000000.0	USD
CY2019Q2	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	2883000	USD
CY2018Q2	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	54000	USD
	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	6327000	USD
	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	4785000	USD
CY2019Q2	us-gaap	Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet	971000	USD
CY2018Q2	us-gaap	Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet	2821000	USD
	us-gaap	Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet	1075000	USD
	us-gaap	Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet	4033000	USD
CY2019Q2	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	1912000	USD
CY2018Q2	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	-2767000	USD
	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	5252000	USD
	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	752000	USD
CY2019Q2	sigi	Unrealized Gains Losseson Equity Securities UnrealizedGainsLossesonEquitySecurities	2115000	USD
CY2018Q2	sigi	Unrealized Gains Losseson Equity Securities UnrealizedGainsLossesonEquitySecurities	1115000	USD
	sigi	Unrealized Gains Losseson Equity Securities UnrealizedGainsLossesonEquitySecurities	12226000	USD
	sigi	Unrealized Gains Losseson Equity Securities UnrealizedGainsLossesonEquitySecurities	-12953000	USD
CY2019Q2	us-gaap	Gain Loss On Investments GainLossOnInvestments	4027000	USD
CY2018Q2	us-gaap	Gain Loss On Investments GainLossOnInvestments	-1652000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	17478000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	-12201000	USD
CY2019Q2	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	2394000	USD
CY2018Q2	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	2301000	USD
	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	11817000	USD
	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	-2662000	USD
CY2019Q2	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	-279000	USD
CY2018Q2	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	-1186000	USD
	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	409000	USD
	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	-10291000	USD
CY2019Q2	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	2115000	USD
CY2018Q2	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	1115000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	12226000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-12953000	USD
CY2019Q2	sigi	Held To Maturity Securities Realized Gain HeldToMaturitySecuritiesRealizedGain	1000	USD
CY2018Q2	sigi	Held To Maturity Securities Realized Gain HeldToMaturitySecuritiesRealizedGain	0	USD
	sigi	Held To Maturity Securities Realized Gain HeldToMaturitySecuritiesRealizedGain	1000	USD
	sigi	Held To Maturity Securities Realized Gain HeldToMaturitySecuritiesRealizedGain	2000	USD
CY2019Q2	sigi	Held To Maturity Securities Disposal Security Realized Loss HeldToMaturitySecuritiesDisposalSecurityRealizedLoss	15000	USD
CY2018Q2	sigi	Held To Maturity Securities Disposal Security Realized Loss HeldToMaturitySecuritiesDisposalSecurityRealizedLoss	0	USD
	sigi	Held To Maturity Securities Disposal Security Realized Loss HeldToMaturitySecuritiesDisposalSecurityRealizedLoss	15000	USD
	sigi	Held To Maturity Securities Disposal Security Realized Loss HeldToMaturitySecuritiesDisposalSecurityRealizedLoss	0	USD
CY2019Q2	us-gaap	Equity Securities Fv Ni Realized Gain EquitySecuritiesFvNiRealizedGain	958000	USD
CY2018Q2	us-gaap	Equity Securities Fv Ni Realized Gain EquitySecuritiesFvNiRealizedGain	1226000	USD
	us-gaap	Equity Securities Fv Ni Realized Gain EquitySecuritiesFvNiRealizedGain	3238000	USD
	us-gaap	Equity Securities Fv Ni Realized Gain EquitySecuritiesFvNiRealizedGain	9625000	USD
CY2019Q2	us-gaap	Equity Securities Fv Ni Realized Loss EquitySecuritiesFvNiRealizedLoss	107000	USD
CY2018Q2	us-gaap	Equity Securities Fv Ni Realized Loss EquitySecuritiesFvNiRealizedLoss	0	USD
	us-gaap	Equity Securities Fv Ni Realized Loss EquitySecuritiesFvNiRealizedLoss	107000	USD
	us-gaap	Equity Securities Fv Ni Realized Loss EquitySecuritiesFvNiRealizedLoss	330000	USD
CY2019Q2	sigi	Short Term Investments Realized Gains ShortTermInvestmentsRealizedGains	2000	USD
CY2018Q2	sigi	Short Term Investments Realized Gains ShortTermInvestmentsRealizedGains	2000	USD
	sigi	Short Term Investments Realized Gains ShortTermInvestmentsRealizedGains	16000	USD
	sigi	Short Term Investments Realized Gains ShortTermInvestmentsRealizedGains	3000	USD
CY2019Q2	sigi	Short Term Investments Realized Losses ShortTermInvestmentsRealizedLosses	1000	USD
CY2018Q2	sigi	Short Term Investments Realized Losses ShortTermInvestmentsRealizedLosses	0	USD
	sigi	Short Term Investments Realized Losses ShortTermInvestmentsRealizedLosses	1000	USD
	sigi	Short Term Investments Realized Losses ShortTermInvestmentsRealizedLosses	4000	USD
CY2019Q2	sigi	Other Investments Realized Gains OtherInvestmentsRealizedGains	0	USD
CY2018Q2	sigi	Other Investments Realized Gains OtherInvestmentsRealizedGains	0	USD
	sigi	Other Investments Realized Gains OtherInvestmentsRealizedGains	7000	USD
	sigi	Other Investments Realized Gains OtherInvestmentsRealizedGains	0	USD
CY2019Q2	sigi	Other Investments Realized Losses OtherInvestmentsRealizedLosses	30000	USD
CY2018Q2	sigi	Other Investments Realized Losses OtherInvestmentsRealizedLosses	0	USD
	sigi	Other Investments Realized Losses OtherInvestmentsRealizedLosses	30000	USD
	sigi	Other Investments Realized Losses OtherInvestmentsRealizedLosses	0	USD
CY2019Q2	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	2883000	USD
CY2018Q2	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	54000	USD
	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	6327000	USD
	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	4785000	USD
CY2019Q2	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	153700000	USD
CY2018Q2	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	262900000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	372200000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	938300000	USD
CY2019Q2	sigi	Proceedsfrom Saleof Equity Securities ProceedsfromSaleofEquitySecurities	26400000	USD
CY2018Q2	sigi	Proceedsfrom Saleof Equity Securities ProceedsfromSaleofEquitySecurities	2900000	USD
	sigi	Proceedsfrom Saleof Equity Securities ProceedsfromSaleofEquitySecurities	30100000	USD
	sigi	Proceedsfrom Saleof Equity Securities ProceedsfromSaleofEquitySecurities	43600000	USD
CY2019Q2	us-gaap	Finance Lease Liability FinanceLeaseLiability	1109000	USD
CY2018Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	0	USD
CY2019Q2	us-gaap	Debt Instrument Unamortized Discount Premium And Debt Issuance Costs Net DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet	10331000	USD
CY2019Q2	us-gaap	Long Term Debt And Capital Lease Obligations Including Current Maturities LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities	550778000	USD
CY2018Q4	us-gaap	Long Term Debt LongTermDebt	439540000	USD
CY2019Q2	us-gaap	Long Term Debt Fair Value LongTermDebtFairValue	623655000	USD
CY2018Q4	us-gaap	Long Term Debt Fair Value LongTermDebtFairValue	448622000	USD
CY2019Q2	us-gaap	Finance Lease Liability FinanceLeaseLiability	1109000	USD
CY2018Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	0	USD
CY2019Q2	us-gaap	Long Term Debt And Capital Lease Obligations Including Current Maturities LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities	550778000	USD
CY2018Q4	us-gaap	Long Term Debt LongTermDebt	439540000	USD
CY2019Q2	sigi	Net Asset Value NetAssetValue	45600000	USD
CY2018Q4	sigi	Net Asset Value NetAssetValue	23700000	USD
CY2019Q2	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	33855000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	38317000	USD
CY2019Q2	us-gaap	Direct Premiums Written DirectPremiumsWritten	807367000	USD
CY2018Q2	us-gaap	Direct Premiums Written DirectPremiumsWritten	753363000	USD
	us-gaap	Direct Premiums Written DirectPremiumsWritten	1573761000	USD
	us-gaap	Direct Premiums Written DirectPremiumsWritten	1467597000	USD
CY2019Q2	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	5333000	USD
CY2018Q2	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	6536000	USD
	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	11888000	USD
	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	12807000	USD
CY2019Q2	us-gaap	Ceded Premiums Written CededPremiumsWritten	111303000	USD
CY2018Q2	us-gaap	Ceded Premiums Written CededPremiumsWritten	104651000	USD
	us-gaap	Ceded Premiums Written CededPremiumsWritten	211305000	USD
	us-gaap	Ceded Premiums Written CededPremiumsWritten	200596000	USD
CY2019Q2	us-gaap	Premiums Written Net PremiumsWrittenNet	701397000	USD
CY2018Q2	us-gaap	Premiums Written Net PremiumsWrittenNet	655248000	USD
	us-gaap	Premiums Written Net PremiumsWrittenNet	1374344000	USD
	us-gaap	Premiums Written Net PremiumsWrittenNet	1279808000	USD
CY2019Q2	us-gaap	Direct Premiums Earned DirectPremiumsEarned	740348000	USD
CY2018Q2	us-gaap	Direct Premiums Earned DirectPremiumsEarned	696723000	USD
	us-gaap	Direct Premiums Earned DirectPremiumsEarned	1468385000	USD
	us-gaap	Direct Premiums Earned DirectPremiumsEarned	1380456000	USD
CY2019Q2	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	5742000	USD
CY2018Q2	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	6612000	USD
	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	12304000	USD
	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	12736000	USD
CY2019Q2	us-gaap	Ceded Premiums Earned CededPremiumsEarned	103471000	USD
CY2018Q2	us-gaap	Ceded Premiums Earned CededPremiumsEarned	98499000	USD
	us-gaap	Ceded Premiums Earned CededPremiumsEarned	205497000	USD
	us-gaap	Ceded Premiums Earned CededPremiumsEarned	196528000	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
	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	1275192000	USD
	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	1196664000	USD
CY2019Q2	us-gaap	Policyholder Benefits And Claims Incurred Gross PolicyholderBenefitsAndClaimsIncurredGross	435700000	USD
CY2018Q2	us-gaap	Policyholder Benefits And Claims Incurred Gross PolicyholderBenefitsAndClaimsIncurredGross	391014000	USD
	us-gaap	Policyholder Benefits And Claims Incurred Gross PolicyholderBenefitsAndClaimsIncurredGross	860357000	USD
	us-gaap	Policyholder Benefits And Claims Incurred Gross PolicyholderBenefitsAndClaimsIncurredGross	811930000	USD
CY2019Q2	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Assumed ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed	4348000	USD
CY2018Q2	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Assumed ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed	2364000	USD
	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Assumed ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed	9613000	USD
	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Assumed ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed	10368000	USD
CY2019Q2	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	59064000	USD
CY2018Q2	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	27050000	USD
	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	102407000	USD
	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	71029000	USD
CY2019Q2	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	380984000	USD
CY2018Q2	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	366328000	USD
	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	767563000	USD
	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	751269000	USD
	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:100%;border-collapse:collapse;text-align:left;"><tr><td colspan="8"/></tr><tr><td style="width:74%;"/><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%;"/></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="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;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="6" 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;">Six Months ended June 30,</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;">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;"><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;">2018</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 reserve 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;border-top:1px solid #000000;"><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;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>3,893,868</span></span></div></td><td style="vertical-align:bottom;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;border-top:1px solid #000000;"><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;border-top:1px solid #000000;"><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;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;">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></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 reserve 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;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-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;">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></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>783,938</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>756,855</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>(16,375</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>(5,586</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>767,563</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>751,269</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></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>210,374</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>214,169</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>442,820</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>457,441</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>653,194</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>671,610</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 reserve for loss and loss expense, at end of period</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>3,470,849</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>3,265,044</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 period</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>556,203</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>539,321</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 reserve for loss and loss expense at end of period</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>4,027,052</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>3,804,365</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>
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
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
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
	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	783938000	USD
	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	756855000	USD
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	767563000	USD
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	751269000	USD
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	210374000	USD
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	214169000	USD
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	442820000	USD
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	457441000	USD
	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	653194000	USD
	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	671610000	USD
CY2019Q2	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	3470849000	USD
CY2018Q2	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	3265044000	USD
CY2019Q2	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	556203000	USD
CY2018Q2	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	539321000	USD
CY2019Q2	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	4027052000	USD
CY2018Q2	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	3804365000	USD
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	4
CY2019Q2	us-gaap	Net Investment Income NetInvestmentIncome	58505000	USD
CY2018Q2	us-gaap	Net Investment Income NetInvestmentIncome	45553000	USD
	us-gaap	Net Investment Income NetInvestmentIncome	109123000	USD
	us-gaap	Net Investment Income NetInvestmentIncome	88784000	USD
CY2019Q2	us-gaap	Gain Loss On Investments GainLossOnInvestments	4027000	USD
CY2018Q2	us-gaap	Gain Loss On Investments GainLossOnInvestments	-1652000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	17478000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	-12201000	USD
CY2019Q2	sigi	Total Investment Revenues TotalInvestmentRevenues	62532000	USD
CY2018Q2	sigi	Total Investment Revenues TotalInvestmentRevenues	43901000	USD
	sigi	Total Investment Revenues TotalInvestmentRevenues	126601000	USD
	sigi	Total Investment Revenues TotalInvestmentRevenues	76583000	USD
CY2019Q2	us-gaap	Revenues Revenues	708204000	USD
CY2018Q2	us-gaap	Revenues Revenues	651916000	USD
	us-gaap	Revenues Revenues	1407166000	USD
	us-gaap	Revenues Revenues	1278605000	USD
CY2019Q2	us-gaap	Net Investment Income NetInvestmentIncome	58505000	USD
CY2018Q2	us-gaap	Net Investment Income NetInvestmentIncome	45553000	USD
	us-gaap	Net Investment Income NetInvestmentIncome	109123000	USD
	us-gaap	Net Investment Income NetInvestmentIncome	88784000	USD
CY2019Q2	us-gaap	Gain Loss On Investments GainLossOnInvestments	4027000	USD
CY2018Q2	us-gaap	Gain Loss On Investments GainLossOnInvestments	-1652000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	17478000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	-12201000	USD
CY2019Q2	sigi	Total Investment Revenues TotalInvestmentRevenues	62532000	USD
CY2018Q2	sigi	Total Investment Revenues TotalInvestmentRevenues	43901000	USD
	sigi	Total Investment Revenues TotalInvestmentRevenues	126601000	USD
	sigi	Total Investment Revenues TotalInvestmentRevenues	76583000	USD
CY2019Q2	sigi	Taxoninvestmentincome Taxoninvestmentincome	11729000	USD
CY2018Q2	sigi	Taxoninvestmentincome Taxoninvestmentincome	7617000	USD
	sigi	Taxoninvestmentincome Taxoninvestmentincome	23849000	USD
	sigi	Taxoninvestmentincome Taxoninvestmentincome	12843000	USD
CY2019Q2	sigi	Total Investment Income After Federal Income Tax TotalInvestmentIncomeAfterFederalIncomeTax	50803000	USD
CY2018Q2	sigi	Total Investment Income After Federal Income Tax TotalInvestmentIncomeAfterFederalIncomeTax	36284000	USD
	sigi	Total Investment Income After Federal Income Tax TotalInvestmentIncomeAfterFederalIncomeTax	102752000	USD
	sigi	Total Investment Income After Federal Income Tax TotalInvestmentIncomeAfterFederalIncomeTax	63740000	USD
CY2019Q2	sigi	Total Investment Revenues TotalInvestmentRevenues	62532000	USD
CY2018Q2	sigi	Total Investment Revenues TotalInvestmentRevenues	43901000	USD
	sigi	Total Investment Revenues TotalInvestmentRevenues	126601000	USD
	sigi	Total Investment Revenues TotalInvestmentRevenues	76583000	USD
CY2019Q2	us-gaap	Interest Expense Debt InterestExpenseDebt	7366000	USD
CY2018Q2	us-gaap	Interest Expense Debt InterestExpenseDebt	6125000	USD
	us-gaap	Interest Expense Debt InterestExpenseDebt	18892000	USD
	us-gaap	Interest Expense Debt InterestExpenseDebt	12277000	USD
CY2019Q2	us-gaap	Other General Expense OtherGeneralExpense	9566000	USD
CY2018Q2	us-gaap	Other General Expense OtherGeneralExpense	3283000	USD
	us-gaap	Other General Expense OtherGeneralExpense	21976000	USD
	us-gaap	Other General Expense OtherGeneralExpense	14615000	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
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	163919000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	92456000	USD
CY2019Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	90225000	USD
CY2019Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	17959000	USD
CY2019Q2	us-gaap	Net Income Loss NetIncomeLoss	72266000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	83546000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	17544000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	66002000	USD
CY2019Q2	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Before Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax	21000	USD
CY2019Q2	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax	4000	USD
CY2019Q2	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	17000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	1300000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	273000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	1027000	USD
CY2019Q2	sigi	Total Unrealized Gains Losses On Investment Securities Gross TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross	82225000	USD
CY2019Q2	sigi	Total Unrealized Gains Losses On Investment Securities Tax TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax	17267000	USD
CY2019Q2	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	-64958000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-664000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-140000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-524000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-664000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-140000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-524000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	82889000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	17407000	USD
CY2019Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	65482000	USD
CY2019Q2	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	173114000	USD
CY2019Q2	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	35366000	USD
CY2019Q2	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	137748000	USD
CY2018Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	72525000	USD
CY2018Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	13706000	USD
CY2018Q2	us-gaap	Net Income Loss NetIncomeLoss	58819000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-23993000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-5038000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-18955000	USD
CY2018Q2	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Before Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax	8000	USD
CY2018Q2	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax	2000	USD
CY2018Q2	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	6000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-2870000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	-603000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	-2267000	USD
CY2018Q2	sigi	Total Unrealized Gains Losses On Investment Securities Gross TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross	-21131000	USD
CY2018Q2	sigi	Total Unrealized Gains Losses On Investment Securities Tax TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax	-4437000	USD
CY2018Q2	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	16694000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-531000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-111000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-420000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-531000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-111000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-420000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-20600000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-4326000	USD
CY2018Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-16274000	USD
CY2018Q2	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	51925000	USD
CY2018Q2	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	9380000	USD
CY2018Q2	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	42545000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	163919000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	30305000	USD
	us-gaap	Net Income Loss NetIncomeLoss	133614000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	186472000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	39157000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	147315000	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Before Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax	30000	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax	6000	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	24000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	2377000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	499000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	1878000	USD
	sigi	Total Unrealized Gains Losses On Investment Securities Gross TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross	184065000	USD
	sigi	Total Unrealized Gains Losses On Investment Securities Tax TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax	38652000	USD
	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	-145413000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-1328000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-279000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-1049000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-1328000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-279000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-1049000	USD
	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	185393000	USD
	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	38931000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	146462000	USD
	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	349312000	USD
	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	69236000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	280076000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	92456000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	14712000	USD
	us-gaap	Net Income Loss NetIncomeLoss	77744000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-109308000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-22955000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-86353000	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Before Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax	20000	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax	4000	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	16000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-7419000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	-1558000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	-5861000	USD
	sigi	Total Unrealized Gains Losses On Investment Securities Gross TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross	-101909000	USD
	sigi	Total Unrealized Gains Losses On Investment Securities Tax TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax	-21401000	USD
	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	80508000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-1063000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-223000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-840000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-1063000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-223000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-840000	USD
	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-100846000	USD
	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-21178000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-79668000	USD
	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	-8390000	USD
	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	-6466000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-1924000	USD
	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	0	USD
	sigi	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Non Credit Other Than Temporary Impaired Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForNonCreditOtherThanTemporaryImpairedSecuritiesNetOfTax	0	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	24000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	1878000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-1049000	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
CY2019Q2	us-gaap	Operating Lease Expense OperatingLeaseExpense	2245000	USD
	us-gaap	Operating Lease Expense OperatingLeaseExpense	4397000	USD
CY2019Q2	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	315000	USD
	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	599000	USD
CY2019Q2	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	7000	USD
	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	7000	USD
CY2019Q2	sigi	Finance Lease Expense FinanceLeaseExpense	322000	USD
	sigi	Finance Lease Expense FinanceLeaseExpense	606000	USD
CY2019Q2	us-gaap	Variable Lease Cost VariableLeaseCost	-120000	USD
	us-gaap	Variable Lease Cost VariableLeaseCost	668000	USD
CY2019Q2	us-gaap	Short Term Lease Cost ShortTermLeaseCost	437000	USD
	us-gaap	Short Term Lease Cost ShortTermLeaseCost	1175000	USD
CY2019Q2	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P6Y
CY2019Q2	us-gaap	Finance Lease Weighted Average Remaining Lease Term1 FinanceLeaseWeightedAverageRemainingLeaseTerm1	P2Y
CY2019Q2	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.034
CY2019Q2	us-gaap	Finance Lease Weighted Average Discount Rate Percent FinanceLeaseWeightedAverageDiscountRatePercent	0.018
CY2019Q2	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	29632000	USD
CY2019Q2	us-gaap	Operating Lease Liability OperatingLeaseLiability	30336000	USD
CY2019Q2	us-gaap	Finance Lease Right Of Use Asset FinanceLeaseRightOfUseAsset	1106000	USD
CY2019Q2	us-gaap	Finance Lease Liability FinanceLeaseLiability	1109000	USD
CY2019Q2	us-gaap	Finance Lease Liability Payments Remainder Of Fiscal Year FinanceLeaseLiabilityPaymentsRemainderOfFiscalYear	389000	USD
CY2019Q2	us-gaap	Lessee Operating Lease Liability Payments Remainder Of Fiscal Year LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear	4044000	USD
CY2019Q2	sigi	Total Leases Due Remainderofthe Fiscal Year TotalLeasesDueRemainderoftheFiscalYear	4433000	USD
CY2019Q2	us-gaap	Finance Lease Liability Payments Due Next Twelve Months FinanceLeaseLiabilityPaymentsDueNextTwelveMonths	448000	USD
CY2019Q2	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	7737000	USD
CY2019Q2	sigi	Total Leases Due Next12 Months TotalLeasesDueNext12Months	8185000	USD
CY2019Q2	us-gaap	Finance Lease Liability Payments Due Year Two FinanceLeaseLiabilityPaymentsDueYearTwo	244000	USD
CY2019Q2	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	5483000	USD
CY2019Q2	sigi	Total Leases Due In Two Years TotalLeasesDueInTwoYears	5727000	USD
CY2019Q2	us-gaap	Finance Lease Liability Payments Due Year Three FinanceLeaseLiabilityPaymentsDueYearThree	53000	USD
CY2019Q2	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	3912000	USD
CY2019Q2	sigi	Total Leases Due In Three Years TotalLeasesDueInThreeYears	3965000	USD
CY2019Q2	us-gaap	Finance Lease Liability Payments Due Year Four FinanceLeaseLiabilityPaymentsDueYearFour	0	USD
CY2019Q2	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	2900000	USD
CY2019Q2	sigi	Total Leases Due In Four Years TotalLeasesDueInFourYears	2900000	USD
CY2019Q2	us-gaap	Finance Lease Liability Payments Due Year Five FinanceLeaseLiabilityPaymentsDueYearFive	0	USD
CY2019Q2	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	9698000	USD
CY2019Q2	sigi	Total Leases Due Thereafter TotalLeasesDueThereafter	9698000	USD
CY2019Q2	us-gaap	Finance Lease Liability Payments Due FinanceLeaseLiabilityPaymentsDue	1134000	USD
CY2019Q2	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	33774000	USD
CY2019Q2	sigi	Total Minimum Payment Required TotalMinimumPaymentRequired	34908000	USD
CY2019Q2	us-gaap	Finance Lease Liability Undiscounted Excess Amount FinanceLeaseLiabilityUndiscountedExcessAmount	25000	USD
CY2019Q2	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	3438000	USD
CY2019Q2	sigi	Total Imputed Interest TotalImputedInterest	3463000	USD
CY2019Q2	us-gaap	Finance Lease Liability FinanceLeaseLiability	1109000	USD
CY2019Q2	us-gaap	Operating Lease Liability OperatingLeaseLiability	30336000	USD
CY2019Q2	sigi	Total Lease Liability TotalLeaseLiability	31445000	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 Next12 Months TotalLeasesDueNext12Months	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	Total Leases Due In Two Years TotalLeasesDueInTwoYears	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	Total Leases Due In Three Years TotalLeasesDueInThreeYears	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	Total Leases Due In Four Years TotalLeasesDueInFourYears	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	Total Leases Due In Five Years TotalLeasesDueInFiveYears	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	Total Leases Due Thereafter TotalLeasesDueThereafter	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	Total Minimum Payment Required TotalMinimumPaymentRequired	37330000	USD

Files In Submission

Name	View Source	Status
0000230557-19-000023-index-headers.html	Edgar Link	pending
0000230557-19-000023-index.html	Edgar Link	pending
0000230557-19-000023.txt	Edgar Link	pending
0000230557-19-000023-xbrl.zip	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
R1.htm	Edgar Link	pending
R10.htm	Edgar Link	pending
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R9.htm	Edgar Link	pending
report.css	Edgar Link	pending
Show.js	Edgar Link	pending
sigi-20190630.xsd	Edgar Link	pending
sigi-20190630_cal.xml	Edgar Link	unprocessable
sigi-20190630_def.xml	Edgar Link	unprocessable
sigi-20190630_lab.xml	Edgar Link	unprocessable
sigi-20190630_pre.xml	Edgar Link	unprocessable
sigi-6302019x10q.htm	Edgar Link	pending
sigi-6302019x10q_htm.xml	Edgar Link	completed
sigi-ex116302019xq2.htm	Edgar Link	pending
sigi-ex3116302019xq2.htm	Edgar Link	pending
sigi-ex3126302019xq2.htm	Edgar Link	pending
sigi-ex3216302019xq2.htm	Edgar Link	pending
sigi-ex3226302019xq2.htm	Edgar Link	pending

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$SIGI
Selective Insurance Group Inc Stock $sigi

2019 Q3 Form 10-Q Financial Statement

#000023055719000023 Filed on August 01, 2019

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$SIGI Selective Insurance Group Inc Stock $sigi

2019 Q3 Form 10-Q Financial Statement

#000023055719000023 Filed on August 01, 2019

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$SIGI
Selective Insurance Group Inc Stock $sigi