$SIGI
Selective Insurance Group Inc Stock $sigi

$sigi Overview Financials Valuation SEC Filings Company Website

2021 Q1 Form 10-Q Financial Statement

#000023055721000016 Filed on April 29, 2021

Income Statement

Concept	2021 Q1	2020 Q1
Revenue	$803.9M	$664.8M
YoY Change	20.92%	-4.88%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin	$9.600M	$12.00M
YoY Change	-20.0%	-25.47%
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$149.1M	$136.5M
YoY Change	9.19%	5.26%
% of Gross Profit
Operating Expenses	$660.9M	$641.3M
YoY Change	3.06%	4.5%
Operating Profit
YoY Change
Interest Expense	-$7.400M	-$7.600M
YoY Change	-2.63%	-33.91%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$135.6M	$16.00M
YoY Change	747.86%	-78.29%
Income Tax	$26.36M	$761.0K
% Of Pretax Income	19.44%	4.76%
Net Earnings	$109.3M	$15.24M
YoY Change	617.18%	-75.16%
Net Earnings / Revenue	13.59%	2.29%
Basic Earnings Per Share	$1.78	$0.26
Diluted Earnings Per Share	$1.77	$0.25
COMMON SHARES
Basic Shares Outstanding	59.88M shares	59.67M shares
Diluted Shares Outstanding

Balance Sheet

Concept	2021 Q1	2020 Q1
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$8.916M	$14.61M
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	$76.10M	$80.06M
YoY Change	-4.95%	16.61%
Goodwill	$7.849M	$7.849M
YoY Change	0.0%	0.0%
Intangibles
YoY Change
Long-Term Investments	$7.559B	$6.842B
YoY Change	10.48%	9.76%
Other Assets	$8.400M	$48.30M
YoY Change	-82.61%	14.73%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$9.849B	$8.975B
YoY Change	9.73%	8.36%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$83.70M	$103.4M
YoY Change	-19.05%	-0.19%
Deferred Revenue
YoY Change
Short-Term Debt	$0.00	$302.0M
YoY Change	-100.0%
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$125.7M	$417.8M
YoY Change	-69.91%	256.48%
LONG-TERM LIABILITIES
Long-Term Debt	$550.9M	$550.6M
YoY Change	0.05%	0.09%
Other Long-Term Liabilities	$376.0M	$292.1M
YoY Change	28.72%	15.23%
Total Long-Term Liabilities	$926.9M	$842.7M
YoY Change	9.99%	4.87%
TOTAL LIABILITIES
Total Short-Term Liabilities	$125.7M	$417.8M
Total Long-Term Liabilities	$926.9M	$842.7M
Total Liabilities	$7.105B	$6.879B
YoY Change	3.29%	8.2%
SHAREHOLDERS EQUITY
Retained Earnings	$2.363B	$2.083B
YoY Change	13.43%	9.18%
Common Stock	$655.0M	$635.0M
YoY Change	3.15%	4.9%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$608.7M	$599.8M
YoY Change	1.5%	1.44%
Treasury Stock Shares		44.12M shares
Shareholders Equity	$2.744B	$2.096B
YoY Change
Total Liabilities & Shareholders Equity	$9.849B	$8.975B
YoY Change	9.73%	8.36%

Cashflow Statement

Concept	2021 Q1	2020 Q1
OPERATING ACTIVITIES
Net Income	$109.3M	$15.24M
YoY Change	617.18%	-75.16%
Depreciation, Depletion And Amortization	$149.1M	$136.5M
YoY Change	9.19%	5.26%
Cash From Operating Activities	$130.3M	$39.32M
YoY Change	231.3%	-15.7%
INVESTING ACTIVITIES
Capital Expenditures	$4.561M	$8.416M
YoY Change	-45.81%	5.8%
Acquisitions
YoY Change
Other Investing Activities	-$106.4M	-$307.4M
YoY Change	-65.39%	128.04%
Cash From Investing Activities	-$110.9M	-$315.8M
YoY Change	-64.88%	121.28%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net	$8.845M	$6.928M
YoY Change	27.67%	5.21%
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-$25.64M	$283.1M
YoY Change	-109.05%	215.71%
NET CHANGE
Cash From Operating Activities	$130.3M	$39.32M
Cash From Investing Activities	-$110.9M	-$315.8M
Cash From Financing Activities	-$25.64M	$283.1M
Net Change In Cash	-$6.315M	$6.631M
YoY Change	-195.23%	-203.53%
FREE CASH FLOW
Cash From Operating Activities	$130.3M	$39.32M
Capital Expenditures	$4.561M	$8.416M
Free Cash Flow	$125.7M	$30.90M
YoY Change	306.77%	-20.12%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2021Q1	dei	Amendment Flag AmendmentFlag	false
CY2021Q1	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2021
CY2021Q1	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	Q1
CY2021Q1	dei	Entity Central Index Key EntityCentralIndexKey	0000230557
CY2021Q1	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2021Q1	dei	Document Type DocumentType	10-Q
CY2021Q1	dei	Document Quarterly Report DocumentQuarterlyReport	true
CY2021Q1	dei	Document Period End Date DocumentPeriodEndDate	2021-03-31
CY2021Q1	dei	Document Transition Report DocumentTransitionReport	false
CY2021Q1	dei	Entity File Number EntityFileNumber	001-33067
CY2021Q1	dei	Entity Registrant Name EntityRegistrantName	SELECTIVE INSURANCE GROUP, INC
CY2021Q1	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	NJ
CY2021Q1	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	22-2168890
CY2021Q1	dei	Entity Address Address Line1 EntityAddressAddressLine1	40 Wantage Avenue
CY2021Q1	dei	Entity Address City Or Town EntityAddressCityOrTown	Branchville
CY2021Q1	dei	Entity Address State Or Province EntityAddressStateOrProvince	NJ
CY2021Q1	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	07890
CY2021Q1	dei	City Area Code CityAreaCode	973
CY2021Q1	dei	Local Phone Number LocalPhoneNumber	948-3000
CY2021Q1	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2021Q1	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2021Q1	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2021Q1	dei	Entity Small Business EntitySmallBusiness	false
CY2021Q1	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
CY2021Q1	dei	Entity Shell Company EntityShellCompany	false
CY2021Q1	sigi	Debt Securities Heldtomaturity Gross DebtSecuritiesHeldtomaturityGross	24370000	USD
CY2021Q2	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	60024254	shares
CY2021Q1	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	25204000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	18001000	USD
CY2020Q4	sigi	Debt Securities Heldtomaturity Gross DebtSecuritiesHeldtomaturityGross	16846000	USD
CY2021Q1	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	26000	USD
CY2020Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	22000	USD
CY2021Q1	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	24344000	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	16824000	USD
CY2021Q1	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-8781000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-3969000	USD
CY2021Q1	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	6253077000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	6073517000	USD
CY2021Q1	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	6521641000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	6455928000	USD
CY2021Q1	sigi	Commercialmortgageloanfairvalue Commercialmortgageloanfairvalue	62233000	USD
CY2020Q4	sigi	Commercialmortgageloanfairvalue Commercialmortgageloanfairvalue	47289000	USD
CY2021Q1	sigi	Commercialmortgageloans Gross CommercialmortgageloansGross	61066000	USD
CY2020Q4	sigi	Commercialmortgageloans Gross CommercialmortgageloansGross	46306000	USD
CY2021Q1	us-gaap	Allowance For Loan And Lease Losses Real Estate AllowanceForLoanAndLeaseLossesRealEstate	0	USD
CY2020Q4	us-gaap	Allowance For Loan And Lease Losses Real Estate AllowanceForLoanAndLeaseLossesRealEstate	0	USD
CY2021Q1	us-gaap	Mortgage Loans On Real Estate Commercial And Consumer Net MortgageLoansOnRealEstateCommercialAndConsumerNet	61066000	USD
CY2020Q4	us-gaap	Mortgage Loans On Real Estate Commercial And Consumer Net MortgageLoansOnRealEstateCommercialAndConsumerNet	46306000	USD
CY2021Q1	us-gaap	Equity Securities Fv Ni Cost EquitySecuritiesFvNiCost	304159000	USD
CY2020Q4	us-gaap	Equity Securities Fv Ni Cost EquitySecuritiesFvNiCost	301551000	USD
CY2021Q1	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	324255000	USD
CY2020Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	310367000	USD
CY2021Q1	us-gaap	Other Short Term Investments OtherShortTermInvestments	337807000	USD
CY2020Q4	us-gaap	Other Short Term Investments OtherShortTermInvestments	409852000	USD
CY2021Q1	us-gaap	Other Investments OtherInvestments	290153000	USD
CY2020Q4	us-gaap	Other Investments OtherInvestments	266322000	USD
CY2021Q1	us-gaap	Investments Investments	7559266000	USD
CY2020Q4	us-gaap	Investments Investments	7505599000	USD
CY2021Q1	us-gaap	Cash Cash	488000	USD
CY2020Q4	us-gaap	Cash Cash	394000	USD
CY2021Q1	us-gaap	Restricted Cash RestrictedCash	8428000	USD
CY2020Q4	us-gaap	Restricted Cash RestrictedCash	14837000	USD
CY2021Q1	us-gaap	Accrued Investment Income Receivable AccruedInvestmentIncomeReceivable	46072000	USD
CY2020Q4	us-gaap	Accrued Investment Income Receivable AccruedInvestmentIncomeReceivable	45004000	USD
CY2021Q1	us-gaap	Premiums Receivable Gross PremiumsReceivableGross	916196000	USD
CY2020Q4	us-gaap	Premiums Receivable Gross PremiumsReceivableGross	857014000	USD
CY2021Q1	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	21000000	USD
CY2020Q4	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	21000000	USD
CY2021Q1	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	895196000	USD
CY2020Q4	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	836014000	USD
CY2021Q1	us-gaap	Reinsurance Recoverables On Unpaid Losses Gross ReinsuranceRecoverablesOnUnpaidLossesGross	582696000	USD
CY2020Q4	us-gaap	Reinsurance Recoverables On Unpaid Losses Gross ReinsuranceRecoverablesOnUnpaidLossesGross	589269000	USD
CY2021Q1	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1840000	USD
CY2020Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1777000	USD
CY2021Q1	us-gaap	Reinsurance Recoverables ReinsuranceRecoverables	580856000	USD
CY2020Q4	us-gaap	Reinsurance Recoverables ReinsuranceRecoverables	587492000	USD
CY2021Q1	us-gaap	Prepaid Reinsurance Premiums PrepaidReinsurancePremiums	168575000	USD
CY2020Q4	us-gaap	Prepaid Reinsurance Premiums PrepaidReinsurancePremiums	170531000	USD
CY2021Q1	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	245844000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	240150000	USD
CY2021Q1	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	76096000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	77696000	USD
CY2021Q1	us-gaap	Deferred Policy Acquisition Costs DeferredPolicyAcquisitionCosts	302652000	USD
CY2020Q4	us-gaap	Deferred Policy Acquisition Costs DeferredPolicyAcquisitionCosts	288578000	USD
CY2021Q1	us-gaap	Goodwill Goodwill	7849000	USD
CY2020Q4	us-gaap	Goodwill Goodwill	7849000	USD
CY2021Q1	us-gaap	Other Assets OtherAssets	203134000	USD
CY2020Q4	us-gaap	Other Assets OtherAssets	153919000	USD
CY2021Q1	us-gaap	Assets Assets	9848612000	USD
CY2020Q4	us-gaap	Assets Assets	9687913000	USD
CY2021Q1	us-gaap	Liability For Claims And Claims Adjustment Expense Property Casualty Liability LiabilityForClaimsAndClaimsAdjustmentExpensePropertyCasualtyLiability	4360188000	USD
CY2020Q4	us-gaap	Liability For Claims And Claims Adjustment Expense Property Casualty Liability LiabilityForClaimsAndClaimsAdjustmentExpensePropertyCasualtyLiability	4260355000	USD
CY2021Q1	us-gaap	Unearned Premiums UnearnedPremiums	1689533000	USD
CY2020Q4	us-gaap	Unearned Premiums UnearnedPremiums	1618271000	USD
CY2021Q1	us-gaap	Long Term Debt And Capital Lease Obligations Including Current Maturities LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities	550904000	USD
CY2020Q4	us-gaap	Long Term Debt And Capital Lease Obligations Including Current Maturities LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities	550743000	USD
CY2021Q1	us-gaap	Accrued Income Taxes AccruedIncomeTaxes	41983000	USD
CY2020Q4	us-gaap	Accrued Income Taxes AccruedIncomeTaxes	14021000	USD
CY2021Q1	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	2311000	USD
CY2020Q4	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	27096000	USD
CY2021Q1	us-gaap	Employee Related Liabilities Current And Noncurrent EmployeeRelatedLiabilitiesCurrentAndNoncurrent	83652000	USD
CY2020Q4	us-gaap	Employee Related Liabilities Current And Noncurrent EmployeeRelatedLiabilitiesCurrentAndNoncurrent	114868000	USD
CY2021Q1	us-gaap	Other Liabilities OtherLiabilities	375996000	USD
CY2020Q4	us-gaap	Other Liabilities OtherLiabilities	363670000	USD
CY2021Q1	us-gaap	Liabilities Liabilities	7104567000	USD
CY2020Q4	us-gaap	Liabilities Liabilities	6949024000	USD
CY2021Q1	us-gaap	Preferred Stock Value PreferredStockValue	200000000	USD
CY2020Q4	us-gaap	Preferred Stock Value PreferredStockValue	200000000	USD
CY2021Q1	us-gaap	Common Stock Value CommonStockValue	208576000	USD
CY2020Q4	us-gaap	Common Stock Value CommonStockValue	208066000	USD
CY2021Q1	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	446410000	USD
CY2020Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	438985000	USD
CY2021Q1	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	2363189000	USD
CY2020Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	2271537000	USD
CY2021Q1	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	134600000	USD
CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	220186000	USD
CY2021Q1	us-gaap	Treasury Stock Value TreasuryStockValue	608730000	USD
CY2020Q4	us-gaap	Treasury Stock Value TreasuryStockValue	599885000	USD
CY2021Q1	us-gaap	Stockholders Equity StockholdersEquity	2744045000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	2738889000	USD
CY2021Q1	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2020Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2021Q1	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	9848612000	USD
CY2020Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	9687913000	USD
CY2021Q1	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	724960000	USD
CY2020Q1	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	651703000	USD
CY2021Q1	us-gaap	Net Investment Income NetInvestmentIncome	69716000	USD
CY2020Q1	us-gaap	Net Investment Income NetInvestmentIncome	55967000	USD
CY2021Q1	us-gaap	Gain Loss On Investments GainLossOnInvestments	5119000	USD
CY2020Q1	us-gaap	Gain Loss On Investments GainLossOnInvestments	-44666000	USD
CY2021Q1	us-gaap	Other Income OtherIncome	4112000	USD
CY2020Q1	us-gaap	Other Income OtherIncome	1825000	USD
CY2021Q1	us-gaap	Revenues Revenues	803907000	USD
CY2020Q1	us-gaap	Revenues Revenues	664829000	USD
CY2021Q1	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	413401000	USD
CY2020Q1	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	400324000	USD
CY2021Q1	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	149051000	USD
CY2020Q1	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	136501000	USD
CY2021Q1	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	88910000	USD
CY2020Q1	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	95346000	USD
CY2021Q1	us-gaap	Interest Expense Debt InterestExpenseDebt	7359000	USD
CY2020Q1	us-gaap	Interest Expense Debt InterestExpenseDebt	7601000	USD
CY2021Q1	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	9554000	USD
CY2020Q1	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	9060000	USD
CY2021Q1	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	668275000	USD
CY2020Q1	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	648832000	USD
CY2021Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	135632000	USD
CY2020Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	15997000	USD
CY2021Q1	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	28424000	USD
CY2020Q1	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	9886000	USD
CY2021Q1	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-2062000	USD
CY2020Q1	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-9125000	USD
CY2021Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	26362000	USD
CY2020Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	761000	USD
CY2021Q1	us-gaap	Net Income Loss NetIncomeLoss	109270000	USD
CY2020Q1	us-gaap	Net Income Loss NetIncomeLoss	15236000	USD
CY2021Q1	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	2453000	USD
CY2020Q1	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	0	USD
CY2021Q1	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	106817000	USD
CY2020Q1	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	15236000	USD
CY2021Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.78
CY2020Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.26
CY2021Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.77
CY2020Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.25
CY2021Q1	us-gaap	Net Income Loss NetIncomeLoss	109270000	USD
CY2020Q1	us-gaap	Net Income Loss NetIncomeLoss	15236000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-81613000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-74245000	USD
CY2021Q1	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome	-8943000	USD
CY2021Q1	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	2000	USD
CY2020Q1	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome	-51658000	USD
CY2020Q1	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	-20000	USD
CY2021Q1	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	477000	USD
CY2020Q1	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	8948000	USD
CY2021Q1	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	3948000	USD
CY2020Q1	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	12472000	USD
CY2021Q1	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	86133000	USD
CY2020Q1	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	104463000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-547000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-596000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-547000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-596000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-85586000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-103867000	USD
CY2021Q1	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	23684000	USD
CY2020Q1	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-88631000	USD
CY2021Q1	us-gaap	Stockholders Equity StockholdersEquity	2744045000	USD
CY2020Q1	us-gaap	Stockholders Equity StockholdersEquity	2096456000	USD
CY2021Q1	us-gaap	Preferred Stock Dividends Per Share Declared PreferredStockDividendsPerShareDeclared	306.67
CY2020Q1	us-gaap	Preferred Stock Dividends Per Share Declared PreferredStockDividendsPerShareDeclared	0
CY2021Q1	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.25
CY2020Q1	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.23
CY2020Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	8000	shares
CY2019Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2021Q1	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	8000	shares
CY2020Q1	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2020Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	59905803	shares
CY2019Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	59461153	shares
CY2021Q1	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	6420	shares
CY2020Q1	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	6975	shares
CY2021Q1	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	248459	shares
CY2020Q1	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	341236	shares
CY2021Q1	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	52781	shares
CY2020Q1	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	0	shares
CY2021Q1	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	84018	shares
CY2020Q1	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	101819	shares
CY2021Q1	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	60023883	shares
CY2020Q1	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	59707545	shares
CY2021Q1	us-gaap	Net Income Loss NetIncomeLoss	109270000	USD
CY2020Q1	us-gaap	Net Income Loss NetIncomeLoss	15236000	USD
CY2021Q1	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	13703000	USD
CY2020Q1	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	15415000	USD
CY2021Q1	us-gaap	Share Based Compensation ShareBasedCompensation	6493000	USD
CY2020Q1	us-gaap	Share Based Compensation ShareBasedCompensation	7038000	USD
CY2021Q1	us-gaap	Income Loss From Equity Method Investments Net Of Dividends Or Distributions IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions	13905000	USD
CY2020Q1	us-gaap	Income Loss From Equity Method Investments Net Of Dividends Or Distributions IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions	5602000	USD
CY2021Q1	sigi	Proceedsfromequityinvestmentsinexcessofcurrentyearearnings Proceedsfromequityinvestmentsinexcessofcurrentyearearnings	2309000	USD
CY2020Q1	sigi	Proceedsfromequityinvestmentsinexcessofcurrentyearearnings Proceedsfromequityinvestmentsinexcessofcurrentyearearnings	614000	USD
CY2021Q1	us-gaap	Gain Loss On Investments GainLossOnInvestments	5119000	USD
CY2020Q1	us-gaap	Gain Loss On Investments GainLossOnInvestments	-44666000	USD
CY2021Q1	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	-3000	USD
CY2020Q1	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	-14000	USD
CY2021Q1	sigi	Increase Decrease In Reserves For Losses And Loss Expenses Net Of Reinsurance Recoverables IncreaseDecreaseInReservesForLossesAndLossExpensesNetOfReinsuranceRecoverables	106468000	USD
CY2020Q1	sigi	Increase Decrease In Reserves For Losses And Loss Expenses Net Of Reinsurance Recoverables IncreaseDecreaseInReservesForLossesAndLossExpensesNetOfReinsuranceRecoverables	49077000	USD
CY2021Q1	sigi	Increase Decrease In Unearned Premiums Net Of Prepaid Reinsurance IncreaseDecreaseInUnearnedPremiumsNetOfPrepaidReinsurance	73218000	USD
CY2020Q1	sigi	Increase Decrease In Unearned Premiums Net Of Prepaid Reinsurance IncreaseDecreaseInUnearnedPremiumsNetOfPrepaidReinsurance	-4376000	USD
CY2021Q1	us-gaap	Increase Decrease In Income Taxes IncreaseDecreaseInIncomeTaxes	25927000	USD
CY2020Q1	us-gaap	Increase Decrease In Income Taxes IncreaseDecreaseInIncomeTaxes	276000	USD
CY2021Q1	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	59182000	USD
CY2020Q1	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	-25572000	USD
CY2021Q1	us-gaap	Increase Decrease In Deferred Policy Acquisition Costs IncreaseDecreaseInDeferredPolicyAcquisitionCosts	14074000	USD
CY2020Q1	us-gaap	Increase Decrease In Deferred Policy Acquisition Costs IncreaseDecreaseInDeferredPolicyAcquisitionCosts	-1605000	USD
CY2021Q1	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	1101000	USD
CY2020Q1	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	-880000	USD
CY2021Q1	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	-31216000	USD
CY2020Q1	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	-52722000	USD
CY2021Q1	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	14302000	USD
CY2020Q1	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	-4583000	USD
CY2021Q1	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-68236000	USD
CY2020Q1	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-62959000	USD
CY2021Q1	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	130256000	USD
CY2020Q1	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	39317000	USD
CY2021Q1	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	9000000	USD
CY2020Q1	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	0	USD
CY2021Q1	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	671909000	USD
CY2020Q1	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	319539000	USD
CY2021Q1	sigi	Payments To Acquire Commercial Mortgage Loans PaymentsToAcquireCommercialMortgageLoans	-14860000	USD
CY2020Q1	sigi	Payments To Acquire Commercial Mortgage Loans PaymentsToAcquireCommercialMortgageLoans	-14096000	USD
CY2021Q1	sigi	Paymentsto Acquire Equity Securities PaymentstoAcquireEquitySecurities	48910000	USD
CY2020Q1	sigi	Paymentsto Acquire Equity Securities PaymentstoAcquireEquitySecurities	45511000	USD
CY2021Q1	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	18589000	USD
CY2020Q1	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	27433000	USD
CY2021Q1	us-gaap	Payments To Acquire Short Term Investments PaymentsToAcquireShortTermInvestments	1723212000	USD
CY2020Q1	us-gaap	Payments To Acquire Short Term Investments PaymentsToAcquireShortTermInvestments	2086599000	USD
CY2021Q1	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	212891000	USD
CY2020Q1	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	101671000	USD
CY2021Q1	us-gaap	Proceeds From Sale And Collection Of Mortgage Notes Receivable ProceedsFromSaleAndCollectionOfMortgageNotesReceivable	99000	USD
CY2020Q1	us-gaap	Proceeds From Sale And Collection Of Mortgage Notes Receivable ProceedsFromSaleAndCollectionOfMortgageNotesReceivable	0	USD
CY2021Q1	us-gaap	Proceeds From Sale Of Short Term Investments ProceedsFromSaleOfShortTermInvestments	1795239000	USD
CY2020Q1	us-gaap	Proceeds From Sale Of Short Term Investments ProceedsFromSaleOfShortTermInvestments	1851532000	USD
CY2021Q1	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	1461000	USD
CY2020Q1	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	405000	USD
CY2021Q1	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	319469000	USD
CY2020Q1	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	227686000	USD
CY2021Q1	sigi	Proceedsfrom Saleof Equity Securities ProceedsfromSaleofEquitySecurities	42782000	USD
CY2020Q1	sigi	Proceedsfrom Saleof Equity Securities ProceedsfromSaleofEquitySecurities	1320000	USD
CY2021Q1	us-gaap	Proceeds From Sale Of Other Investments ProceedsFromSaleOfOtherInvestments	3004000	USD
CY2020Q1	us-gaap	Proceeds From Sale Of Other Investments ProceedsFromSaleOfOtherInvestments	0	USD
CY2021Q1	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	5162000	USD
CY2020Q1	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	3152000	USD
CY2021Q1	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	4561000	USD
CY2020Q1	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	8416000	USD
CY2021Q1	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-110934000	USD
CY2020Q1	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-315828000	USD
CY2021Q1	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	2453000	USD
CY2020Q1	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	0	USD
CY2021Q1	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	14569000	USD
CY2020Q1	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	13313000	USD
CY2021Q1	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	8845000	USD
CY2020Q1	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	6928000	USD
CY2021Q1	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	824000	USD
CY2021Q1	us-gaap	Proceeds From Issuance Of Preferred Stock And Preference Stock ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	-479000	USD
CY2020Q1	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	1525000	USD
CY2020Q1	us-gaap	Proceeds From Issuance Of Preferred Stock And Preference Stock ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	0	USD
CY2021Q1	us-gaap	Proceeds From Debt Net Of Issuance Costs ProceedsFromDebtNetOfIssuanceCosts	0	USD
CY2020Q1	us-gaap	Proceeds From Debt Net Of Issuance Costs ProceedsFromDebtNetOfIssuanceCosts	387000000	USD
CY2021Q1	us-gaap	Repayments Of Debt RepaymentsOfDebt	0	USD
CY2020Q1	us-gaap	Repayments Of Debt RepaymentsOfDebt	85000000	USD
CY2021Q1	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	115000	USD
CY2020Q1	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	142000	USD
CY2021Q1	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-25637000	USD
CY2020Q1	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	283142000	USD
CY2021Q1	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect	-6315000	USD
CY2020Q1	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect	6631000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	15231000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	7975000	USD
CY2021Q1	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	8916000	USD
CY2020Q1	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	14606000	USD
CY2021Q1	sigi	Interest Paid Operatingand Investing Activities InterestPaidOperatingandInvestingActivities	8722000	USD
CY2020Q1	sigi	Interest Paid Operatingand Investing Activities InterestPaidOperatingandInvestingActivities	8854000	USD
CY2021Q1	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	0	USD
CY2020Q1	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	0	USD
CY2021Q1	us-gaap	Operating Lease Payments OperatingLeasePayments	2226000	USD
CY2020Q1	us-gaap	Operating Lease Payments OperatingLeasePayments	2130000	USD
CY2021Q1	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	2000	USD
CY2020Q1	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	6000	USD
CY2021Q1	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	115000	USD
CY2020Q1	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	142000	USD
CY2021Q1	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	183000	USD
CY2020Q1	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	29000	USD
CY2021Q1	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	16000	USD
CY2020Q1	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	3828000	USD
CY2021Q1	us-gaap	Noncash Or Part Noncash Acquisition Fixed Assets Acquired1 NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1	3000	USD
CY2020Q1	us-gaap	Noncash Or Part Noncash Acquisition Fixed Assets Acquired1 NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1	5000	USD
CY2021Q1	us-gaap	Cash Cash	488000	USD
CY2020Q4	us-gaap	Cash Cash	394000	USD
CY2021Q1	us-gaap	Restricted Cash RestrictedCash	8428000	USD
CY2020Q4	us-gaap	Restricted Cash RestrictedCash	14837000	USD
CY2021Q1	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	8916000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	15231000	USD
CY2021Q1	us-gaap	Available For Sale Securities Amortized Cost AvailableForSaleSecuritiesAmortizedCost	6253077000	USD
CY2021Q1	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-8781000	USD
CY2021Q1	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	297474000	USD
CY2021Q1	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	20129000	USD
CY2021Q1	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	6521641000	USD
CY2020Q4	us-gaap	Available For Sale Securities Amortized Cost AvailableForSaleSecuritiesAmortizedCost	6073517000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-3969000	USD
CY2020Q4	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	397922000	USD
CY2020Q4	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	11542000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	6455928000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-3969000	USD
CY2021Q1	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not Previously Recorded DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded	5667000	USD
CY2021Q1	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not To Sell Before Recovery Credit Loss Previously Recorded Expense Reversal DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal	-677000	USD
CY2021Q1	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Securities Sold DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold	-178000	USD
CY2021Q1	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Sell Before Recovery DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery	0	USD
CY2021Q1	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-8781000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	0	USD
CY2020Q1	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not Previously Recorded DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded	15787000	USD
CY2020Q1	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not To Sell Before Recovery Credit Loss Previously Recorded Expense Reversal DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal	0	USD
CY2020Q1	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Securities Sold DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold	0	USD
CY2020Q1	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Sell Before Recovery DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery	0	USD
CY2020Q1	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-15787000	USD
CY2021Q1	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	453772000	USD
CY2021Q1	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	1057000	USD
CY2021Q1	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	1065000	USD
CY2021Q1	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	3400223000	USD
CY2021Q1	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	14433000	USD
CY2021Q1	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	15325000	USD
CY2021Q1	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	2043563000	USD
CY2021Q1	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	8854000	USD
CY2021Q1	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	8814000	USD
CY2021Q1	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	624083000	USD
CY2021Q1	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	0	USD
CY2021Q1	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	0	USD
CY2021Q1	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	6521641000	USD
CY2021Q1	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	24344000	USD
CY2021Q1	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	25204000	USD
CY2021Q1	us-gaap	Assets Held By Insurance Regulators AssetsHeldByInsuranceRegulators	26000000.0	USD
CY2021Q1	us-gaap	Security Owned And Pledged As Collateral Fair Value SecurityOwnedAndPledgedAsCollateralFairValue	317200000	USD
CY2021Q1	sigi	Maximumexposuretocreditconcentrationriskofthe Companysstockholdersequityotherthancertain U.S.Governmentagencies MaximumexposuretocreditconcentrationriskoftheCompanysstockholdersequityotherthancertainU.S.governmentagencies	0.10
CY2020Q4	sigi	Maximumexposuretocreditconcentrationriskofthe Companysstockholdersequityotherthancertain U.S.Governmentagencies MaximumexposuretocreditconcentrationriskoftheCompanysstockholdersequityotherthancertainU.S.governmentagencies	0.10
CY2021Q1	us-gaap	Investment Income Investment Expense InvestmentIncomeInvestmentExpense	3627000	USD
CY2020Q1	us-gaap	Investment Income Investment Expense InvestmentIncomeInvestmentExpense	3408000	USD
CY2021Q1	us-gaap	Net Investment Income NetInvestmentIncome	69716000	USD
CY2020Q1	us-gaap	Net Investment Income NetInvestmentIncome	55967000	USD
CY2021Q1	sigi	Debt And Equity Securities Realized Gains DebtAndEquitySecuritiesRealizedGains	3676000	USD
CY2020Q1	sigi	Debt And Equity Securities Realized Gains DebtAndEquitySecuritiesRealizedGains	5676000	USD
CY2021Q1	sigi	Debt And Equity Securities Realized Losses DebtAndEquitySecuritiesRealizedLosses	4471000	USD
CY2020Q1	sigi	Debt And Equity Securities Realized Losses DebtAndEquitySecuritiesRealizedLosses	1576000	USD
CY2021Q1	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	-795000	USD
CY2020Q1	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	4100000	USD
CY2021Q1	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	11280000	USD
CY2020Q1	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-17137000	USD
CY2021Q1	sigi	Losses On Investment Securities For Which We Have The Intent To Sell LossesOnInvestmentSecuritiesForWhichWeHaveTheIntentToSell	362000	USD
CY2020Q1	sigi	Losses On Investment Securities For Which We Have The Intent To Sell LossesOnInvestmentSecuritiesForWhichWeHaveTheIntentToSell	15602000	USD
CY2021Q1	us-gaap	Gain Loss On Investments GainLossOnInvestments	5119000	USD
CY2020Q1	us-gaap	Gain Loss On Investments GainLossOnInvestments	-44666000	USD
CY2021Q1	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	10097000	USD
CY2020Q1	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	-17140000	USD
CY2021Q1	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	1183000	USD
CY2020Q1	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	3000	USD
CY2021Q1	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	11280000	USD
CY2020Q1	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-17137000	USD
CY2021Q1	us-gaap	Long Term Debt Fair Value LongTermDebtFairValue	643157000	USD
CY2020Q4	us-gaap	Long Term Debt Fair Value LongTermDebtFairValue	695596000	USD
CY2021Q1	us-gaap	Finance Lease Liability FinanceLeaseLiability	577000	USD
CY2020Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	508000	USD
CY2021Q1	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	550904000	USD
CY2020Q4	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	550743000	USD
CY2021Q1	sigi	Net Asset Value NetAssetValue	53500000	USD
CY2020Q4	sigi	Net Asset Value NetAssetValue	46800000	USD
CY2021Q1	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	25204000	USD
CY2021Q1	sigi	Commercialmortgageloanfairvalue Commercialmortgageloanfairvalue	62233000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	18001000	USD
CY2020Q4	sigi	Commercialmortgageloanfairvalue Commercialmortgageloanfairvalue	47289000	USD
CY2020Q4	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	21000000	USD
CY2019Q4	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	6400000	USD
CY2020Q1	sigi	Premiums Receivable Allowance Net Of Writeoffs PremiumsReceivableAllowanceNetOfWriteoffs	10500000	USD
CY2021Q1	us-gaap	Reinsurance Recoverables On Unpaid Losses Gross ReinsuranceRecoverablesOnUnpaidLossesGross	582696000	USD
CY2021Q1	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1840000	USD
CY2021Q1	us-gaap	Reinsurance Recoverables ReinsuranceRecoverables	580856000	USD
CY2021Q1	us-gaap	Reinsurance Recoverable Credit Quality Indicator Date Updated ReinsuranceRecoverableCreditQualityIndicatorDateUpdated	2021-03-31
CY2020Q4	us-gaap	Reinsurance Recoverables On Unpaid Losses Gross ReinsuranceRecoverablesOnUnpaidLossesGross	589269000	USD
CY2020Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1777000	USD
CY2020Q4	us-gaap	Reinsurance Recoverables ReinsuranceRecoverables	587492000	USD
CY2020Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1777000	USD
CY2019Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	4400000	USD
CY2021Q1	us-gaap	Reinsurance Recoverable Credit Loss Expense Reversal ReinsuranceRecoverableCreditLossExpenseReversal	63000	USD
CY2020Q1	us-gaap	Reinsurance Recoverable Credit Loss Expense Reversal ReinsuranceRecoverableCreditLossExpenseReversal	5000	USD
CY2021Q1	us-gaap	Reinsurance Loss On Uncollectible Accounts In Period Amount ReinsuranceLossOnUncollectibleAccountsInPeriodAmount	0	USD
CY2020Q1	us-gaap	Reinsurance Loss On Uncollectible Accounts In Period Amount ReinsuranceLossOnUncollectibleAccountsInPeriodAmount	0	USD
CY2021Q1	us-gaap	Reinsurance Recoverable Allowance For Credit Loss Recovery ReinsuranceRecoverableAllowanceForCreditLossRecovery	0	USD
CY2020Q1	us-gaap	Reinsurance Recoverable Allowance For Credit Loss Recovery ReinsuranceRecoverableAllowanceForCreditLossRecovery	0	USD
CY2021Q1	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1840000	USD
CY2020Q1	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1502000	USD
CY2021Q1	sigi	Change In Direct Premiums Written ChangeInDirectPremiumsWritten	162000000	USD
CY2021Q1	sigi	Change In Direct Premiums Written Percentage ChangeInDirectPremiumsWrittenPercentage	0.22
CY2021Q1	us-gaap	Schedule Of Liability For Unpaid Claims And Claims Adjustment Expense ScheduleOfLiabilityForUnpaidClaimsAndClaimsAdjustmentExpense	<table style="border-collapse:collapse;display:inline-table;vertical-align:top;width:100.000%"><tr><td style="width:1.0%"/><td style="width:74.046%"/><td style="width:0.1%"/><td style="width:0.1%"/><td style="width:0.530%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:10.595%"/><td style="width:0.1%"/><td style="width:0.1%"/><td style="width:0.530%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:10.599%"/><td style="width:0.1%"/></tr><tr><td colspan="3" style="border-top:1pt solid #000000;padding:0 1pt"/><td colspan="3" style="border-top:1pt solid #000000;padding:0 1pt"/><td colspan="9" style="border-top:1pt solid #000000;padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">Quarter ended March 31,</span></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">($ in thousands)</span></td><td colspan="3" style="padding:0 1pt"/><td colspan="3" style="border-top:1pt solid #000000;padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">2021</span></td><td colspan="3" style="border-top:1pt solid #000000;padding:0 1pt"/><td colspan="3" style="border-top:1pt solid #000000;padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">2020</span></td></tr><tr><td colspan="3" style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Gross reserve for loss and loss expense, at beginning of year</span></td><td colspan="3" style="background-color:#ccffcc;border-top:1pt solid #000000;padding:0 1pt"/><td style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">$</span></td><td style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">4,260,355</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"/><td colspan="2" style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">4,067,163 </span></td><td style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><div><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Less: reinsurance recoverable on unpaid loss and loss expense, at beginning of year</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:5.2pt;font-weight:400;line-height:100%;position:relative;top:-2.8pt;vertical-align:baseline">1</span></div></td><td colspan="3" style="padding:0 1pt"/><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">554,269</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="padding:0 1pt"/><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">547,066 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#ccffcc;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Net reserve for loss and loss expense, at beginning of year</span></td><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"/><td colspan="2" style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">3,706,086</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"/><td colspan="2" style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">3,520,097 </span></td><td style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Incurred loss and loss expense for claims occurring in the:</span></td><td colspan="3" style="padding:0 1pt"/><td colspan="3" style="border-top:1pt solid #000000;padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%"> </span></td><td colspan="3" style="padding:0 1pt"/><td colspan="3" style="border-top:1pt solid #000000;padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td></tr><tr><td colspan="3" style="background-color:#ccffcc;padding:2px 1pt 2px 7.75pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Current year</span></td><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"/><td colspan="2" style="background-color:#ccffcc;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">447,170</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ccffcc;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"/><td colspan="2" style="background-color:#ccffcc;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">407,276 </span></td><td style="background-color:#ccffcc;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="padding:2px 1pt 2px 7.75pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Prior years</span></td><td colspan="3" style="padding:0 1pt"/><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">(33,769)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="padding:0 1pt"/><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">(6,952)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#ccffcc;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Total incurred loss and loss expense</span></td><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"/><td colspan="2" style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">413,401</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"/><td colspan="2" style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">400,324 </span></td><td style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Paid loss and loss expense for claims occurring in the:</span></td><td colspan="3" style="padding:0 1pt"/><td colspan="3" style="border-top:1pt solid #000000;padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%"> </span></td><td colspan="3" style="padding:0 1pt"/><td colspan="3" style="border-top:1pt solid #000000;padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td></tr><tr><td colspan="3" style="background-color:#ccffcc;padding:2px 1pt 2px 7.75pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Current year</span></td><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"/><td colspan="2" style="background-color:#ccffcc;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">80,158</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ccffcc;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"/><td colspan="2" style="background-color:#ccffcc;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">70,610 </span></td><td style="background-color:#ccffcc;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="padding:2px 1pt 2px 7.75pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Prior years</span></td><td colspan="3" style="padding:0 1pt"/><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">243,687</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="padding:0 1pt"/><td colspan="2" style="padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">281,736 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#ccffcc;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Total paid loss and loss expense</span></td><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"/><td colspan="2" style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">323,845</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"/><td colspan="2" style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">352,346 </span></td><td style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Net reserve for loss and loss expense, at end of period</span></td><td colspan="3" style="padding:0 1pt"/><td colspan="2" style="border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">3,795,642</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="padding:0 1pt"/><td colspan="2" style="border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">3,568,075 </span></td><td style="border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#d0ffd0;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Add: Reinsurance recoverable on unpaid loss and loss expense, at end of period</span></td><td colspan="3" style="background-color:#d0ffd0;padding:0 1pt"/><td colspan="2" style="background-color:#d0ffd0;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">564,546</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#d0ffd0;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#d0ffd0;padding:0 1pt"/><td colspan="2" style="background-color:#d0ffd0;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">535,560 </span></td><td style="background-color:#d0ffd0;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Gross reserve for loss and loss expense at end of period</span></td><td colspan="3" style="padding:0 1pt"/><td style="border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">$</span></td><td style="border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">4,360,188</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="padding:0 1pt"/><td colspan="2" style="border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">4,103,635 </span></td><td style="border-bottom:3pt double #000000;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr></table><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:5.2pt;font-weight:400;line-height:120%;position:relative;top:-2.8pt;vertical-align:baseline">1</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:120%">First Quarter 2020 includes an adjustment of $2.9 million related to our adoption of ASU 2016-13, </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-style:italic;font-weight:400;line-height:120%">Financial Instruments - Credit Losses</span>.
CY2020Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	4260355000	USD
CY2019Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	4067163000	USD
CY2020Q4	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	554269000	USD
CY2019Q4	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	547066000	USD
CY2020Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	3706086000	USD
CY2019Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	3520097000	USD
CY2021Q1	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	447170000	USD
CY2020Q1	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	407276000	USD
CY2021Q1	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	413401000	USD
CY2020Q1	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	400324000	USD
CY2021Q1	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	80158000	USD
CY2020Q1	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	70610000	USD
CY2021Q1	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	243687000	USD
CY2020Q1	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	281736000	USD
CY2021Q1	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	323845000	USD
CY2020Q1	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	352346000	USD
CY2021Q1	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	3795642000	USD
CY2020Q1	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	3568075000	USD
CY2021Q1	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	564546000	USD
CY2020Q1	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	535560000	USD
CY2021Q1	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	4360188000	USD
CY2020Q1	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	4103635000	USD
CY2021Q1	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	4
CY2021Q1	us-gaap	Net Investment Income NetInvestmentIncome	69716000	USD
CY2020Q1	us-gaap	Net Investment Income NetInvestmentIncome	55967000	USD
CY2021Q1	us-gaap	Gain Loss On Investments GainLossOnInvestments	5119000	USD
CY2020Q1	us-gaap	Gain Loss On Investments GainLossOnInvestments	-44666000	USD
CY2021Q1	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	74835000	USD
CY2020Q1	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	11301000	USD
CY2021Q1	us-gaap	Revenues Revenues	803907000	USD
CY2020Q1	us-gaap	Revenues Revenues	664829000	USD
CY2021Q1	us-gaap	Net Investment Income NetInvestmentIncome	69716000	USD
CY2020Q1	us-gaap	Net Investment Income NetInvestmentIncome	55967000	USD
CY2021Q1	us-gaap	Gain Loss On Investments GainLossOnInvestments	5119000	USD
CY2020Q1	us-gaap	Gain Loss On Investments GainLossOnInvestments	-44666000	USD
CY2021Q1	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	74835000	USD
CY2020Q1	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	11301000	USD
CY2021Q1	sigi	Taxoninvestmentincome Taxoninvestmentincome	14448000	USD
CY2020Q1	sigi	Taxoninvestmentincome Taxoninvestmentincome	1104000	USD
CY2021Q1	sigi	Totalinvestmentsegmentincomeafterfederalincometax Totalinvestmentsegmentincomeafterfederalincometax	60387000	USD
CY2020Q1	sigi	Totalinvestmentsegmentincomeafterfederalincometax Totalinvestmentsegmentincomeafterfederalincometax	10197000	USD
CY2021Q1	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	74835000	USD
CY2020Q1	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	11301000	USD
CY2021Q1	us-gaap	Interest Expense Debt InterestExpenseDebt	7359000	USD
CY2020Q1	us-gaap	Interest Expense Debt InterestExpenseDebt	7601000	USD
CY2021Q1	us-gaap	Other General Expense OtherGeneralExpense	9554000	USD
CY2020Q1	us-gaap	Other General Expense OtherGeneralExpense	9060000	USD
CY2021Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	135632000	USD
CY2020Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	15997000	USD
CY2021Q1	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	2453000	USD
CY2020Q1	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	0	USD
CY2021Q1	sigi	Income Available To Common Stockholders Before Tax IncomeAvailableToCommonStockholdersBeforeTax	133179000	USD
CY2020Q1	sigi	Income Available To Common Stockholders Before Tax IncomeAvailableToCommonStockholdersBeforeTax	15997000	USD
CY2021Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	135632000	USD
CY2021Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	26362000	USD
CY2021Q1	us-gaap	Net Income Loss NetIncomeLoss	109270000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-103308000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-21695000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-81613000	USD
CY2021Q1	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income Gross NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeGross	-11320000	USD
CY2021Q1	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income Tax NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeTax	-2377000	USD
CY2021Q1	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome	-8943000	USD
CY2021Q1	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Before Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax	2000	USD
CY2021Q1	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax	0	USD
CY2021Q1	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	2000	USD
CY2021Q1	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securitiesbefore Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesbeforeTax	604000	USD
CY2021Q1	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesTax	127000	USD
CY2021Q1	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	477000	USD
CY2021Q1	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Gross DebtSecuritiesAvailableforsaleAllowanceforCreditLossGross	4997000	USD
CY2021Q1	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Tax DebtSecuritiesAvailableforsaleAllowanceforCreditLossTax	1049000	USD
CY2021Q1	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	3948000	USD
CY2021Q1	sigi	Total Unrealized Gains Losses On Investment Securities Gross TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross	-109029000	USD
CY2021Q1	sigi	Total Unrealized Gains Losses On Investment Securities Tax TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax	-22896000	USD
CY2021Q1	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	86133000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-693000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-146000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-547000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-693000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-146000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-547000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-108336000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-22750000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-85586000	USD
CY2021Q1	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	27296000	USD
CY2021Q1	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	3612000	USD
CY2021Q1	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	23684000	USD
CY2020Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	15997000	USD
CY2020Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	761000	USD
CY2020Q1	us-gaap	Net Income Loss NetIncomeLoss	15236000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-93981000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-19736000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-74245000	USD
CY2020Q1	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income Gross NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeGross	-65390000	USD
CY2020Q1	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income Tax NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeTax	-13732000	USD
CY2020Q1	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome	-51658000	USD
CY2020Q1	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Before Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax	-25000	USD
CY2020Q1	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax	-5000	USD
CY2020Q1	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	-20000	USD
CY2020Q1	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securitiesbefore Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesbeforeTax	11327000	USD
CY2020Q1	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesTax	2379000	USD
CY2020Q1	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	8948000	USD
CY2020Q1	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Gross DebtSecuritiesAvailableforsaleAllowanceforCreditLossGross	15787000	USD
CY2020Q1	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Tax DebtSecuritiesAvailableforsaleAllowanceforCreditLossTax	3315000	USD
CY2020Q1	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	12472000	USD
CY2020Q1	sigi	Total Unrealized Gains Losses On Investment Securities Gross TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross	-132232000	USD
CY2020Q1	sigi	Total Unrealized Gains Losses On Investment Securities Tax TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax	-27769000	USD
CY2020Q1	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	104463000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-754000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-158000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-596000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-754000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-158000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-596000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-131478000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-27611000	USD
CY2020Q1	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-103867000	USD
CY2020Q1	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	-115481000	USD
CY2020Q1	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	-26850000	USD
CY2020Q1	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-88631000	USD
CY2021Q1	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-547000	USD
CY2020Q4	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	100000000	USD
CY2021Q1	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	52781	shares
CY2021Q1	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	3400000	USD
CY2021Q1	us-gaap	Stock Repurchase Program Remaining Authorized Repurchase Amount1 StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1	96600000	USD

Files In Submission

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$SIGI
Selective Insurance Group Inc Stock $sigi

2021 Q1 Form 10-Q Financial Statement

#000023055721000016 Filed on April 29, 2021

Income Statement

Balance Sheet

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Files In Submission

$SIGI Selective Insurance Group Inc Stock $sigi

2021 Q1 Form 10-Q Financial Statement

#000023055721000016 Filed on April 29, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$SIGI
Selective Insurance Group Inc Stock $sigi