$SIGI
Selective Insurance Group Inc Stock $sigi

$sigi Overview Financials Valuation SEC Filings Company Website

2021 Q4 Form 10-Q Financial Statement

#000023055721000033 Filed on October 28, 2021

Income Statement

Concept	2021 Q4	2021 Q3	2020 Q3
Revenue	$870.5M	$865.0M	$776.6M
YoY Change	9.02%	11.39%	9.31%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin	$5.369M	$4.270M	$3.900M
YoY Change	-11.98%	9.49%	-54.65%
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$14.40M	$160.9M	$142.3M
YoY Change	-3.98%	13.06%	4.19%
% of Gross Profit
Operating Expenses	$738.7M	$765.2M	$683.5M
YoY Change	16.89%	11.95%	8.18%
Operating Profit
YoY Change
Interest Expense	-$5.147M	-$10.35M	-$7.800M
YoY Change	-31.37%	32.73%	5.41%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$123.8M	$92.64M	$85.26M
YoY Change	-22.13%	8.66%	19.78%
Income Tax	$24.87M	$18.93M	$15.38M
% Of Pretax Income	20.08%	20.44%	18.04%
Net Earnings	$98.98M	$73.71M	$69.88M
YoY Change	-22.1%	5.48%	24.44%
Net Earnings / Revenue	11.37%	8.52%	9.0%
Basic Earnings Per Share		$1.19	$1.17
Diluted Earnings Per Share	$1.619M	$1.18	$1.16
COMMON SHARES
Basic Shares Outstanding	60.12M shares	60.11M shares	59.81M shares
Diluted Shares Outstanding		60.59M shares

Balance Sheet

Concept	2021 Q4	2021 Q3	2020 Q3
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$45.06M	$34.79M	$15.90M
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	$82.05M	$75.01M	$78.44M
YoY Change	5.61%	-4.37%	2.64%
Goodwill	$7.849M	$7.849M	$7.849M
YoY Change	0.63%	0.0%	0.0%
Intangibles
YoY Change
Long-Term Investments	$8.027B	$7.859B	$7.278B
YoY Change	6.95%	7.99%	11.08%
Other Assets	$44.61M	$34.31M	$15.10M
YoY Change	201.41%	127.23%	-0.66%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$10.46B	$10.44B	$9.515B
YoY Change	7.98%	9.75%	9.12%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$158.4M	$113.7M	$93.10M
YoY Change	1.18%	22.14%	-28.22%
Deferred Revenue
YoY Change
Short-Term Debt	$0.00	$0.00	$167.0M
YoY Change		-100.0%
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$158.4M	$113.7M	$260.1M
YoY Change	-7.12%	-56.28%	96.45%
LONG-TERM LIABILITIES
Long-Term Debt	$506.1M	$500.9M	$550.6M
YoY Change	-8.11%	-9.03%	-0.02%
Other Long-Term Liabilities	$416.6M	$444.6M	$346.4M
YoY Change	29.37%	28.36%	26.79%
Total Long-Term Liabilities	$922.6M	$945.5M	$897.0M
YoY Change	5.72%	5.41%	8.87%
TOTAL LIABILITIES
Total Short-Term Liabilities	$158.4M	$113.7M	$260.1M
Total Long-Term Liabilities	$922.6M	$945.5M	$897.0M
Total Liabilities	$7.479B	$7.520B	$7.121B
YoY Change	7.62%	5.6%	8.19%
SHAREHOLDERS EQUITY
Retained Earnings	$2.603B	$2.524B	$2.160B
YoY Change	14.61%	16.86%	7.31%
Common Stock	$673.2M	$666.9M	$646.8M
YoY Change	4.05%	3.11%	4.46%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$608.9M	$608.9M	$599.9M
YoY Change	1.51%	1.5%	1.2%
Treasury Stock Shares	44.27M shares		44.13M shares
Shareholders Equity	$2.983B	$2.922B	$2.394B
YoY Change
Total Liabilities & Shareholders Equity	$10.46B	$10.44B	$9.515B
YoY Change	7.98%	9.75%	9.12%

Cashflow Statement

Concept	2021 Q4	2021 Q3	2020 Q3
OPERATING ACTIVITIES
Net Income	$98.98M	$73.71M	$69.88M
YoY Change	-22.1%	5.48%	24.44%
Depreciation, Depletion And Amortization	$14.40M	$160.9M	$142.3M
YoY Change	-3.98%	13.06%	4.19%
Cash From Operating Activities	$228.1M	$250.9M	$183.5M
YoY Change	31.78%	36.7%	21.44%
INVESTING ACTIVITIES
Capital Expenditures	-$7.040M	-$5.632M	-$5.300M
YoY Change	67.62%	6.26%	-28.38%
Acquisitions
YoY Change
Other Investing Activities	-$194.0M	-$153.4M	-$70.20M
YoY Change	4.29%	118.58%	-45.41%
Cash From Investing Activities	-$201.0M	-$159.1M	-$75.50M
YoY Change	5.69%	110.69%	-44.49%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-16.83M	-66.24M	-97.80M
YoY Change	-202.59%	-32.27%	676.19%
NET CHANGE
Cash From Operating Activities	228.1M	250.9M	183.5M
Cash From Investing Activities	-201.0M	-159.1M	-75.50M
Cash From Financing Activities	-16.83M	-66.24M	-97.80M
Net Change In Cash	10.27M	25.54M	10.20M
YoY Change	-1567.71%	150.35%	308.0%
FREE CASH FLOW
Cash From Operating Activities	$228.1M	$250.9M	$183.5M
Capital Expenditures	-$7.040M	-$5.632M	-$5.300M
Free Cash Flow	$235.2M	$256.5M	$188.8M
YoY Change	32.63%	35.85%	19.12%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
	dei	Amendment Flag AmendmentFlag	false
	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2021
	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	Q3
	dei	Entity Central Index Key EntityCentralIndexKey	0000230557
	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
	dei	Document Type DocumentType	10-Q
	dei	Document Quarterly Report DocumentQuarterlyReport	true
	dei	Document Period End Date DocumentPeriodEndDate	2021-09-30
	dei	Document Transition Report DocumentTransitionReport	false
	dei	Entity File Number EntityFileNumber	001-33067
	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 Filer Category EntityFilerCategory	Large Accelerated Filer
	dei	Entity Address City Or Town EntityAddressCityOrTown	Branchville
	dei	City Area Code CityAreaCode	973
	dei	Entity Address State Or Province EntityAddressStateOrProvince	NJ
	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	07890
	dei	Local Phone Number LocalPhoneNumber	948-3000
	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
	dei	Entity Small Business EntitySmallBusiness	false
	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
	dei	Entity Shell Company EntityShellCompany	false
CY2021Q4	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	60123535	shares
CY2021Q3	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	26037000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	18001000	USD
CY2021Q3	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	25323000	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	16846000	USD
CY2021Q3	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	71000	USD
CY2020Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	22000	USD
CY2021Q3	us-gaap	Debt Securities Held To Maturity Amortized Cost After Allowance For Credit Loss DebtSecuritiesHeldToMaturityAmortizedCostAfterAllowanceForCreditLoss	25252000	USD
CY2020Q4	us-gaap	Debt Securities Held To Maturity Amortized Cost After Allowance For Credit Loss DebtSecuritiesHeldToMaturityAmortizedCostAfterAllowanceForCreditLoss	16824000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-3969000	USD
CY2021Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	6401167000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	6073517000	USD
CY2021Q3	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	6677070000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	6455928000	USD
CY2021Q3	sigi	Commercialmortgageloanfairvalue Commercialmortgageloanfairvalue	86001000	USD
CY2020Q4	sigi	Commercialmortgageloanfairvalue Commercialmortgageloanfairvalue	47289000	USD
CY2021Q3	sigi	Commercialmortgageloans Gross CommercialmortgageloansGross	83993000	USD
CY2020Q4	sigi	Commercialmortgageloans Gross CommercialmortgageloansGross	46306000	USD
CY2021Q3	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
CY2021Q3	us-gaap	Mortgage Loans On Real Estate Commercial And Consumer Net MortgageLoansOnRealEstateCommercialAndConsumerNet	83993000	USD
CY2020Q4	us-gaap	Mortgage Loans On Real Estate Commercial And Consumer Net MortgageLoansOnRealEstateCommercialAndConsumerNet	46306000	USD
CY2021Q3	us-gaap	Equity Securities Fv Ni Cost EquitySecuritiesFvNiCost	299541000	USD
CY2020Q4	us-gaap	Equity Securities Fv Ni Cost EquitySecuritiesFvNiCost	301551000	USD
CY2021Q3	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	324186000	USD
CY2020Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	310367000	USD
CY2021Q3	us-gaap	Other Short Term Investments OtherShortTermInvestments	355937000	USD
CY2020Q4	us-gaap	Other Short Term Investments OtherShortTermInvestments	409852000	USD
CY2021Q3	us-gaap	Other Investments OtherInvestments	392788000	USD
CY2020Q4	us-gaap	Other Investments OtherInvestments	266322000	USD
CY2021Q3	us-gaap	Investments Investments	7859226000	USD
CY2020Q4	us-gaap	Investments Investments	7505599000	USD
CY2021Q3	us-gaap	Cash Cash	477000	USD
CY2020Q4	us-gaap	Cash Cash	394000	USD
CY2021Q3	us-gaap	Restricted Cash RestrictedCash	34312000	USD
CY2020Q4	us-gaap	Restricted Cash RestrictedCash	14837000	USD
CY2021Q3	us-gaap	Accrued Investment Income Receivable AccruedInvestmentIncomeReceivable	46082000	USD
CY2020Q4	us-gaap	Accrued Investment Income Receivable AccruedInvestmentIncomeReceivable	45004000	USD
CY2021Q3	us-gaap	Premiums Receivable Gross PremiumsReceivableGross	1001331000	USD
CY2020Q4	us-gaap	Premiums Receivable Gross PremiumsReceivableGross	857014000	USD
CY2021Q3	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	16500000	USD
CY2020Q4	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	21000000	USD
CY2021Q3	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	984831000	USD
CY2020Q4	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	836014000	USD
CY2021Q3	us-gaap	Reinsurance Recoverables On Unpaid Losses Gross ReinsuranceRecoverablesOnUnpaidLossesGross	687812000	USD
CY2020Q4	us-gaap	Reinsurance Recoverables On Unpaid Losses Gross ReinsuranceRecoverablesOnUnpaidLossesGross	589269000	USD
CY2021Q3	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1595000	USD
CY2020Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1777000	USD
CY2021Q3	us-gaap	Reinsurance Recoverables ReinsuranceRecoverables	686217000	USD
CY2020Q4	us-gaap	Reinsurance Recoverables ReinsuranceRecoverables	587492000	USD
CY2021Q3	us-gaap	Prepaid Reinsurance Premiums PrepaidReinsurancePremiums	187969000	USD
CY2020Q4	us-gaap	Prepaid Reinsurance Premiums PrepaidReinsurancePremiums	170531000	USD
CY2021Q3	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	1220000	USD
CY2020Q4	us-gaap	Income Taxes Receivable IncomeTaxesReceivable	0	USD
CY2021Q3	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	256826000	USD
CY2020Q4	us-gaap	Long Term Debt And Capital Lease Obligations Including Current Maturities LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities	550743000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	240150000	USD
CY2021Q3	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	75014000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	77696000	USD
CY2021Q3	us-gaap	Deferred Policy Acquisition Costs DeferredPolicyAcquisitionCosts	333995000	USD
CY2020Q4	us-gaap	Deferred Policy Acquisition Costs DeferredPolicyAcquisitionCosts	288578000	USD
CY2021Q3	us-gaap	Goodwill Goodwill	7849000	USD
CY2020Q4	us-gaap	Goodwill Goodwill	7849000	USD
CY2021Q3	us-gaap	Other Assets OtherAssets	224982000	USD
CY2020Q4	us-gaap	Other Assets OtherAssets	153919000	USD
CY2021Q3	us-gaap	Assets Assets	10442174000	USD
CY2020Q4	us-gaap	Assets Assets	9687913000	USD
CY2021Q3	us-gaap	Liability For Claims And Claims Adjustment Expense Property Casualty Liability LiabilityForClaimsAndClaimsAdjustmentExpensePropertyCasualtyLiability	4610340000	USD
CY2020Q4	us-gaap	Liability For Claims And Claims Adjustment Expense Property Casualty Liability LiabilityForClaimsAndClaimsAdjustmentExpensePropertyCasualtyLiability	4260355000	USD
CY2021Q3	us-gaap	Unearned Premiums UnearnedPremiums	1847273000	USD
CY2020Q4	us-gaap	Unearned Premiums UnearnedPremiums	1618271000	USD
CY2021Q3	us-gaap	Long Term Debt And Capital Lease Obligations Including Current Maturities LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities	500904000	USD
CY2021Q3	us-gaap	Accrued Income Taxes AccruedIncomeTaxes	0	USD
CY2020Q4	us-gaap	Accrued Income Taxes AccruedIncomeTaxes	14021000	USD
CY2021Q3	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	3215000	USD
CY2020Q4	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	27096000	USD
CY2021Q3	us-gaap	Employee Related Liabilities Current And Noncurrent EmployeeRelatedLiabilitiesCurrentAndNoncurrent	113708000	USD
CY2020Q4	us-gaap	Employee Related Liabilities Current And Noncurrent EmployeeRelatedLiabilitiesCurrentAndNoncurrent	114868000	USD
CY2021Q3	us-gaap	Other Liabilities OtherLiabilities	444638000	USD
CY2020Q4	us-gaap	Other Liabilities OtherLiabilities	363670000	USD
CY2021Q3	us-gaap	Liabilities Liabilities	7520078000	USD
CY2020Q4	us-gaap	Liabilities Liabilities	6949024000	USD
CY2021Q3	us-gaap	Preferred Stock Value PreferredStockValue	200000000	USD
CY2020Q4	us-gaap	Preferred Stock Value PreferredStockValue	200000000	USD
CY2021Q3	us-gaap	Common Stock Value CommonStockValue	208778000	USD
CY2020Q4	us-gaap	Common Stock Value CommonStockValue	208066000	USD
CY2021Q3	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	458143000	USD
CY2020Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	438985000	USD
CY2021Q3	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	2523810000	USD
CY2020Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	2271537000	USD
CY2021Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	140224000	USD
CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	220186000	USD
CY2021Q3	us-gaap	Treasury Stock Value TreasuryStockValue	608859000	USD
CY2020Q4	us-gaap	Treasury Stock Value TreasuryStockValue	599885000	USD
CY2021Q3	us-gaap	Stockholders Equity StockholdersEquity	2922096000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	2738889000	USD
CY2021Q3	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2020Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2021Q3	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	10442174000	USD
CY2020Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	9687913000	USD
CY2021Q3	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	767247000	USD
CY2020Q3	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	694541000	USD
	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	2232725000	USD
	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	1976915000	USD
CY2021Q3	us-gaap	Net Investment Income NetInvestmentIncome	93032000	USD
CY2020Q3	us-gaap	Net Investment Income NetInvestmentIncome	68185000	USD
	us-gaap	Net Investment Income NetInvestmentIncome	246479000	USD
	us-gaap	Net Investment Income NetInvestmentIncome	158596000	USD
CY2021Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	177000	USD
CY2020Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	7721000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	15353000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	-24296000	USD
CY2021Q3	us-gaap	Other Income OtherIncome	4588000	USD
CY2020Q3	us-gaap	Other Income OtherIncome	6119000	USD
	us-gaap	Other Income OtherIncome	14912000	USD
	us-gaap	Other Income OtherIncome	12627000	USD
CY2021Q3	us-gaap	Revenues Revenues	865044000	USD
CY2020Q3	us-gaap	Revenues Revenues	776566000	USD
	us-gaap	Revenues Revenues	2509469000	USD
	us-gaap	Revenues Revenues	2123842000	USD
	us-gaap	Interest Expense Debt InterestExpenseDebt	23310000	USD
CY2021Q3	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	505269000	USD
CY2020Q3	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	447802000	USD
	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	1340293000	USD
	us-gaap	Incurred Claims Property Casualty And Liability IncurredClaimsPropertyCasualtyAndLiability	1252075000	USD
CY2021Q3	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	160868000	USD
CY2020Q3	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	142291000	USD
	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	464276000	USD
	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	415723000	USD
CY2021Q3	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	94759000	USD
CY2020Q3	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	89530000	USD
	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	278531000	USD
	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	269477000	USD
CY2021Q3	us-gaap	Interest Expense Debt InterestExpenseDebt	7242000	USD
CY2020Q3	us-gaap	Interest Expense Debt InterestExpenseDebt	7781000	USD
	us-gaap	Interest Expense Debt InterestExpenseDebt	21967000	USD
CY2021Q3	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	4270000	USD
CY2020Q3	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	3905000	USD
	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	22936000	USD
	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	19310000	USD
CY2021Q3	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	772408000	USD
CY2020Q3	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	691309000	USD
	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	2128003000	USD
	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	1979895000	USD
CY2021Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	92636000	USD
CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	85257000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	381466000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	143947000	USD
CY2021Q3	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	18878000	USD
CY2020Q3	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	17412000	USD
CY2021Q3	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	53000	USD
	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	79319000	USD
	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	25948000	USD
CY2020Q3	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-2030000	USD
	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-2711000	USD
	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-1295000	USD
CY2021Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	18931000	USD
CY2020Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	15382000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	76608000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	24653000	USD
CY2021Q3	us-gaap	Net Income Loss NetIncomeLoss	73705000	USD
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	69875000	USD
	us-gaap	Net Income Loss NetIncomeLoss	304858000	USD
	us-gaap	Net Income Loss NetIncomeLoss	119294000	USD
CY2021Q3	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	2300000	USD
CY2020Q3	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	0	USD
	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	7053000	USD
	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	0	USD
CY2021Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	71405000	USD
CY2020Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	69875000	USD
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	297805000	USD
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	119294000	USD
CY2021Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.19
CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.17
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.95
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.99
CY2021Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.18
CY2020Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.16
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.92
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.98
CY2021Q3	us-gaap	Net Income Loss NetIncomeLoss	73705000	USD
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	69875000	USD
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	-501000	USD
	us-gaap	Net Income Loss NetIncomeLoss	304858000	USD
	us-gaap	Net Income Loss NetIncomeLoss	119294000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-27875000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	29889000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-81402000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	104771000	USD
CY2021Q3	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome	-1851000	USD
CY2020Q3	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome	7299000	USD
	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome	-2906000	USD
	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome	-14751000	USD
CY2021Q3	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	-1000	USD
CY2020Q3	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	0	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	3000	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	5000	USD
CY2021Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	-1024000	USD
CY2020Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	-406000	USD
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	7210000	USD
CY2021Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	1054000	USD
CY2020Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	-2254000	USD
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	3207000	USD
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	6328000	USD
CY2021Q3	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	29695000	USD
CY2020Q3	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	-34528000	USD
	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	81605000	USD
	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	-103553000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-548000	USD
CY2020Q3	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
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-1643000	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	-1787000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-548000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-596000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-1643000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-1787000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-29147000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	35124000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-79962000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	105340000	USD
CY2021Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	44558000	USD
CY2020Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	104999000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	224896000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	224634000	USD
CY2021Q3	us-gaap	Stockholders Equity StockholdersEquity	2922096000	USD
CY2020Q3	us-gaap	Stockholders Equity StockholdersEquity	2393613000	USD
CY2021Q3	us-gaap	Stockholders Equity StockholdersEquity	2922096000	USD
CY2020Q3	us-gaap	Stockholders Equity StockholdersEquity	2393613000	USD
CY2021Q3	us-gaap	Preferred Stock Dividends Per Share Declared PreferredStockDividendsPerShareDeclared	287.50
CY2020Q3	us-gaap	Preferred Stock Dividends Per Share Declared PreferredStockDividendsPerShareDeclared	0
	us-gaap	Preferred Stock Dividends Per Share Declared PreferredStockDividendsPerShareDeclared	881.67
	us-gaap	Preferred Stock Dividends Per Share Declared PreferredStockDividendsPerShareDeclared	0
CY2021Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.25
CY2020Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.23
	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.75
	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.69
CY2021Q2	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	8000	shares
CY2020Q2	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2020Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	8000	shares
CY2019Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2021Q3	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	8000	shares
CY2020Q3	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2021Q3	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	8000	shares
CY2020Q3	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2021Q2	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	60106236	shares
CY2020Q2	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	59811742	shares
CY2020Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	59905803	shares
CY2019Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	59461153	shares
CY2021Q3	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	5096	shares
CY2020Q3	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	7026	shares
	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	17152	shares
	us-gaap	Stock Issued During Period Shares Dividend Reinvestment Plan StockIssuedDuringPeriodSharesDividendReinvestmentPlan	21900	shares
CY2021Q3	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	12946	shares
CY2020Q3	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	16936	shares
	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	339061	shares
	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	455537	shares
CY2021Q3	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	0	shares
CY2020Q3	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	0	shares
	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	52781	shares
	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	0	shares
CY2021Q3	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	743	shares
CY2020Q3	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	1002	shares
	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	85700	shares
	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	103888	shares
CY2021Q3	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	60123535	shares
CY2020Q3	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	59834702	shares
CY2021Q3	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	60123535	shares
CY2020Q3	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	59834702	shares
	us-gaap	Net Income Loss NetIncomeLoss	304858000	USD
	us-gaap	Net Income Loss NetIncomeLoss	119294000	USD
	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	40706000	USD
	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	44435000	USD
	us-gaap	Share Based Compensation ShareBasedCompensation	13431000	USD
	us-gaap	Share Based Compensation ShareBasedCompensation	13935000	USD
	us-gaap	Income Loss From Equity Method Investments Net Of Dividends Or Distributions IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions	65215000	USD
	us-gaap	Income Loss From Equity Method Investments Net Of Dividends Or Distributions IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions	5146000	USD
	sigi	Proceedsfromequityinvestmentsinexcessofcurrentyearearnings Proceedsfromequityinvestmentsinexcessofcurrentyearearnings	2750000	USD
	sigi	Proceedsfromequityinvestmentsinexcessofcurrentyearearnings Proceedsfromequityinvestmentsinexcessofcurrentyearearnings	3136000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	15353000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	-24296000	USD
	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	-50000	USD
	us-gaap	Gain Loss On Disposition Of Assets1 GainLossOnDispositionOfAssets1	-17000	USD
	sigi	Increase Decrease In Reserves For Losses And Loss Expenses Net Of Reinsurance Recoverables IncreaseDecreaseInReservesForLossesAndLossExpensesNetOfReinsuranceRecoverables	251260000	USD
	sigi	Increase Decrease In Reserves For Losses And Loss Expenses Net Of Reinsurance Recoverables IncreaseDecreaseInReservesForLossesAndLossExpensesNetOfReinsuranceRecoverables	190796000	USD
	sigi	Increase Decrease In Unearned Premiums Net Of Prepaid Reinsurance IncreaseDecreaseInUnearnedPremiumsNetOfPrepaidReinsurance	211564000	USD
	sigi	Increase Decrease In Unearned Premiums Net Of Prepaid Reinsurance IncreaseDecreaseInUnearnedPremiumsNetOfPrepaidReinsurance	114672000	USD
	us-gaap	Increase Decrease In Income Taxes IncreaseDecreaseInIncomeTaxes	-17866000	USD
	us-gaap	Increase Decrease In Income Taxes IncreaseDecreaseInIncomeTaxes	-10775000	USD
	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	148817000	USD
	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	28239000	USD
	us-gaap	Increase Decrease In Deferred Policy Acquisition Costs IncreaseDecreaseInDeferredPolicyAcquisitionCosts	45417000	USD
	us-gaap	Increase Decrease In Deferred Policy Acquisition Costs IncreaseDecreaseInDeferredPolicyAcquisitionCosts	21523000	USD
	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	1249000	USD
	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	1507000	USD
	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	-1160000	USD
	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	-33677000	USD
	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	22045000	USD
	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	23388000	USD
	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	35806000	USD
	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-5443000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	543303000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	380883000	USD
	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	11250000	USD
	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	0	USD
	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	1660798000	USD
	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	1373226000	USD
	sigi	Payments To Acquire Commercial Mortgage Loans PaymentsToAcquireCommercialMortgageLoans	-38129000	USD
	sigi	Payments To Acquire Commercial Mortgage Loans PaymentsToAcquireCommercialMortgageLoans	-29800000	USD
	us-gaap	Payments To Acquire Equity Securities Fv Ni PaymentsToAcquireEquitySecuritiesFvNi	82223000	USD
	us-gaap	Payments To Acquire Equity Securities Fv Ni PaymentsToAcquireEquitySecuritiesFvNi	87307000	USD
	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	63661000	USD
	us-gaap	Proceeds From Debt Net Of Issuance Costs ProceedsFromDebtNetOfIssuanceCosts	0	USD
	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	61051000	USD
	us-gaap	Payments To Acquire Short Term Investments PaymentsToAcquireShortTermInvestments	3443597000	USD
	us-gaap	Payments To Acquire Short Term Investments PaymentsToAcquireShortTermInvestments	4475128000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	384586000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	411263000	USD
	us-gaap	Proceeds From Sale And Collection Of Mortgage Notes Receivable ProceedsFromSaleAndCollectionOfMortgageNotesReceivable	442000	USD
	us-gaap	Proceeds From Sale And Collection Of Mortgage Notes Receivable ProceedsFromSaleAndCollectionOfMortgageNotesReceivable	109000	USD
	us-gaap	Proceeds From Sale Of Short Term Investments ProceedsFromSaleOfShortTermInvestments	3497243000	USD
	us-gaap	Proceeds From Sale Of Short Term Investments ProceedsFromSaleOfShortTermInvestments	4377024000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	2735000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	1646000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	910741000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	738238000	USD
	us-gaap	Proceeds From Sale Of Equity Securities Fv Ni ProceedsFromSaleOfEquitySecuritiesFvNi	85373000	USD
	us-gaap	Proceeds From Sale Of Equity Securities Fv Ni ProceedsFromSaleOfEquitySecuritiesFvNi	1320000	USD
	us-gaap	Proceeds From Sale Of Other Investments ProceedsFromSaleOfOtherInvestments	5377000	USD
	us-gaap	Proceeds From Sale Of Other Investments ProceedsFromSaleOfOtherInvestments	3879000	USD
	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	10524000	USD
	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	12890000	USD
	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	15123000	USD
	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	17858000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-417760000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-498001000	USD
	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	7053000	USD
	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	0	USD
	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	43756000	USD
	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	39972000	USD
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	8974000	USD
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	7039000	USD
	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	4575000	USD
	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	5478000	USD
	us-gaap	Proceeds From Issuance Of Preferred Stock And Preference Stock ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	-479000	USD
	us-gaap	Proceeds From Issuance Of Preferred Stock And Preference Stock ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	0	USD
	us-gaap	Proceeds From Debt Net Of Issuance Costs ProceedsFromDebtNetOfIssuanceCosts	487000000	USD
	us-gaap	Repayments Of Debt RepaymentsOfDebt	50000000	USD
	us-gaap	Repayments Of Debt RepaymentsOfDebt	320000000	USD
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	298000	USD
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	429000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-105985000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	125038000	USD
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect	19558000	USD
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect	7920000	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
CY2021Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	34789000	USD
CY2020Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	15895000	USD
	sigi	Interest Paid Operatingand Investing Activities InterestPaidOperatingandInvestingActivities	23278000	USD
	sigi	Interest Paid Operatingand Investing Activities InterestPaidOperatingandInvestingActivities	24449000	USD
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	93000000	USD
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	34000000	USD
	us-gaap	Operating Lease Payments OperatingLeasePayments	6480000	USD
	us-gaap	Operating Lease Payments OperatingLeasePayments	7077000	USD
	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	5000	USD
	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	13000	USD
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	298000	USD
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	429000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	183000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	119000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	273000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	22104000	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	9000	USD
CY2021Q3	us-gaap	Cash Cash	477000	USD
CY2020Q4	us-gaap	Cash Cash	394000	USD
CY2021Q3	us-gaap	Restricted Cash RestrictedCash	34312000	USD
CY2020Q4	us-gaap	Restricted Cash RestrictedCash	14837000	USD
CY2021Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	34789000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	15231000	USD
CY2021Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	6401167000	USD
CY2021Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-7169000	USD
CY2021Q3	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	293966000	USD
CY2021Q3	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	10894000	USD
CY2021Q3	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	6677070000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	6073517000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-3969000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	397922000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	11542000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	6455928000	USD
CY2021Q2	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-6011000	USD
CY2021Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not Previously Recorded DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded	1666000	USD
CY2021Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not To Sell Before Recovery Credit Loss Previously Recorded Expense Reversal DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal	-333000	USD
CY2021Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Securities Sold DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold	-95000	USD
CY2021Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Sell Before Recovery DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery	-80000	USD
CY2021Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-7169000	USD
CY2020Q2	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-10395000	USD
CY2020Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not Previously Recorded DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded	1025000	USD
CY2020Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not To Sell Before Recovery Credit Loss Previously Recorded Expense Reversal DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal	-3856000	USD
CY2020Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Securities Sold DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold	-362000	USD
CY2020Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Sell Before Recovery DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery	-22000	USD
CY2020Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-7180000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-3969000	USD
	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not Previously Recorded DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded	5139000	USD
	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not To Sell Before Recovery Credit Loss Previously Recorded Expense Reversal DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal	-1087000	USD
	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Securities Sold DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold	-711000	USD
	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Sell Before Recovery DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery	-141000	USD
CY2021Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-7169000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	0	USD
	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not Previously Recorded DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded	8100000	USD
	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
	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Securities Sold DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold	-830000	USD
	us-gaap	Schedule Of Liability For Unpaid Claims And Claims Adjustment Expense ScheduleOfLiabilityForUnpaidClaimsAndClaimsAdjustmentExpense	<table style="border-collapse:collapse;display:inline-table;margin-bottom:5pt;vertical-align:text-bottom;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%">Nine Months ended September 30,</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%">1,408,240</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%">1,295,285 </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%">(67,947)</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%">(43,210)</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%">1,340,293</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%">1,252,075 </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%">430,288</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%">421,981 </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%">675,782</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%">646,974 </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%">1,106,070</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%">1,068,955 </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%">3,940,309</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%">3,703,217 </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%">670,031</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%">590,059 </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%">4,610,340</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%">4,293,276 </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%"> Nine Months 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>.
	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Sell Before Recovery DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery	-90000	USD
CY2020Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	-7180000	USD
CY2021Q3	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	511751000	USD
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	32000	USD
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	33000	USD
CY2021Q3	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	3389351000	USD
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	14548000	USD
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	15340000	USD
CY2021Q3	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	2101275000	USD
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	10672000	USD
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	10664000	USD
CY2021Q3	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	674693000	USD
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	0	USD
CY2021Q3	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	0	USD
CY2021Q3	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	6677070000	USD
CY2021Q3	us-gaap	Debt Securities Held To Maturity Amortized Cost After Allowance For Credit Loss DebtSecuritiesHeldToMaturityAmortizedCostAfterAllowanceForCreditLoss	25252000	USD
CY2021Q3	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	26037000	USD
CY2021Q3	us-gaap	Assets Held By Insurance Regulators AssetsHeldByInsuranceRegulators	26100000	USD
CY2021Q3	us-gaap	Security Owned And Pledged As Collateral Fair Value SecurityOwnedAndPledgedAsCollateralFairValue	159900000	USD
CY2021Q3	sigi	Maximumexposuretocreditconcentrationriskofthe Companysstockholdersequityotherthancertain U.S.Governmentagencies MaximumexposuretocreditconcentrationriskoftheCompanysstockholdersequityotherthancertainU.S.governmentagencies	0.10
CY2020Q4	sigi	Maximumexposuretocreditconcentrationriskofthe Companysstockholdersequityotherthancertain U.S.Governmentagencies MaximumexposuretocreditconcentrationriskoftheCompanysstockholdersequityotherthancertainU.S.governmentagencies	0.10
CY2020Q3	sigi	Debt And Equity Securities Realized Gains DebtAndEquitySecuritiesRealizedGains	2975000	USD
CY2021Q3	us-gaap	Investment Income Investment Expense InvestmentIncomeInvestmentExpense	5218000	USD
CY2020Q3	us-gaap	Investment Income Investment Expense InvestmentIncomeInvestmentExpense	4208000	USD
	us-gaap	Investment Income Investment Expense InvestmentIncomeInvestmentExpense	14314000	USD
	us-gaap	Investment Income Investment Expense InvestmentIncomeInvestmentExpense	11004000	USD
CY2021Q3	us-gaap	Net Investment Income NetInvestmentIncome	93032000	USD
CY2020Q3	us-gaap	Net Investment Income NetInvestmentIncome	68185000	USD
	us-gaap	Net Investment Income NetInvestmentIncome	246479000	USD
	us-gaap	Net Investment Income NetInvestmentIncome	158596000	USD
CY2021Q3	sigi	Debt And Equity Securities Realized Gains DebtAndEquitySecuritiesRealizedGains	7151000	USD
	sigi	Debt And Equity Securities Realized Gains DebtAndEquitySecuritiesRealizedGains	12906000	USD
	sigi	Debt And Equity Securities Realized Gains DebtAndEquitySecuritiesRealizedGains	15129000	USD
CY2021Q3	sigi	Debt And Equity Securities Realized Losses DebtAndEquitySecuritiesRealizedLosses	2505000	USD
CY2020Q3	sigi	Debt And Equity Securities Realized Losses DebtAndEquitySecuritiesRealizedLosses	2402000	USD
	sigi	Debt And Equity Securities Realized Losses DebtAndEquitySecuritiesRealizedLosses	8787000	USD
	sigi	Debt And Equity Securities Realized Losses DebtAndEquitySecuritiesRealizedLosses	7841000	USD
CY2021Q3	us-gaap	Debt And Equity Securities Realized Gain Loss DebtAndEquitySecuritiesRealizedGainLoss	4646000	USD
CY2020Q3	us-gaap	Debt And Equity Securities Realized Gain Loss DebtAndEquitySecuritiesRealizedGainLoss	573000	USD
	us-gaap	Debt And Equity Securities Realized Gain Loss DebtAndEquitySecuritiesRealizedGainLoss	4119000	USD
	us-gaap	Debt And Equity Securities Realized Gain Loss DebtAndEquitySecuritiesRealizedGainLoss	7288000	USD
CY2021Q3	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-3111000	USD
CY2020Q3	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	4338000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	15830000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-7098000	USD
CY2021Q3	sigi	Losses On Investment Securities For Which We Have The Intent To Sell LossesOnInvestmentSecuritiesForWhichWeHaveTheIntentToSell	30000	USD
CY2020Q3	sigi	Losses On Investment Securities For Which We Have The Intent To Sell LossesOnInvestmentSecuritiesForWhichWeHaveTheIntentToSell	44000	USD
	sigi	Losses On Investment Securities For Which We Have The Intent To Sell LossesOnInvestmentSecuritiesForWhichWeHaveTheIntentToSell	483000	USD
	sigi	Losses On Investment Securities For Which We Have The Intent To Sell LossesOnInvestmentSecuritiesForWhichWeHaveTheIntentToSell	16259000	USD
CY2021Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	177000	USD
CY2020Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	7721000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	15353000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	-24296000	USD
CY2021Q3	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	269000	USD
CY2020Q3	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	4338000	USD
	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	14767000	USD
	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	-7101000	USD
CY2021Q3	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	-3380000	USD
CY2020Q3	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	0	USD
	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	1063000	USD
	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	3000	USD
CY2021Q3	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-3111000	USD
CY2020Q3	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	4338000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	15830000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-7098000	USD
CY2021Q3	us-gaap	Long Term Debt Fair Value LongTermDebtFairValue	640304000	USD
CY2020Q4	us-gaap	Long Term Debt Fair Value LongTermDebtFairValue	695596000	USD
CY2021Q3	us-gaap	Finance Lease Liability FinanceLeaseLiability	394000	USD
CY2020Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	508000	USD
CY2021Q3	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	500904000	USD
CY2020Q4	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	550743000	USD
CY2021Q3	sigi	Net Asset Value NetAssetValue	96200000	USD
CY2020Q4	sigi	Net Asset Value NetAssetValue	46800000	USD
CY2021Q3	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	26037000	USD
CY2021Q3	sigi	Commercialmortgageloanfairvalue Commercialmortgageloanfairvalue	86001000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	18001000	USD
CY2020Q4	sigi	Commercialmortgageloanfairvalue Commercialmortgageloanfairvalue	47289000	USD
CY2021Q2	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	18300000	USD
CY2020Q2	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	21000000	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
	sigi	Premiums Receivable Allowance Net Of Writeoffs PremiumsReceivableAllowanceNetOfWriteoffs	13500000	USD
CY2021Q3	us-gaap	Reinsurance Recoverables On Unpaid Losses Gross ReinsuranceRecoverablesOnUnpaidLossesGross	687812000	USD
CY2021Q3	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1595000	USD
CY2021Q3	us-gaap	Reinsurance Recoverables ReinsuranceRecoverables	686217000	USD
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
CY2021Q3	sigi	Change In Total Reinsurance Recoverables Net ChangeInTotalReinsuranceRecoverablesNet	98700000	USD
CY2021Q2	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1777000	USD
CY2020Q2	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	2396000	USD
CY2020Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1777000	USD
CY2019Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	4400000	USD
CY2021Q3	us-gaap	Reinsurance Recoverable Credit Loss Expense Reversal ReinsuranceRecoverableCreditLossExpenseReversal	-182000	USD
CY2020Q3	us-gaap	Reinsurance Recoverable Credit Loss Expense Reversal ReinsuranceRecoverableCreditLossExpenseReversal	-565000	USD
	us-gaap	Reinsurance Recoverable Credit Loss Expense Reversal ReinsuranceRecoverableCreditLossExpenseReversal	-182000	USD
	us-gaap	Reinsurance Recoverable Credit Loss Expense Reversal ReinsuranceRecoverableCreditLossExpenseReversal	334000	USD
CY2021Q3	us-gaap	Reinsurance Loss On Uncollectible Accounts In Period Amount ReinsuranceLossOnUncollectibleAccountsInPeriodAmount	0	USD
CY2020Q3	us-gaap	Reinsurance Loss On Uncollectible Accounts In Period Amount ReinsuranceLossOnUncollectibleAccountsInPeriodAmount	0	USD
	us-gaap	Reinsurance Loss On Uncollectible Accounts In Period Amount ReinsuranceLossOnUncollectibleAccountsInPeriodAmount	0	USD
	us-gaap	Reinsurance Loss On Uncollectible Accounts In Period Amount ReinsuranceLossOnUncollectibleAccountsInPeriodAmount	0	USD
CY2021Q3	us-gaap	Reinsurance Recoverable Allowance For Credit Loss Recovery ReinsuranceRecoverableAllowanceForCreditLossRecovery	0	USD
CY2020Q3	us-gaap	Reinsurance Recoverable Allowance For Credit Loss Recovery ReinsuranceRecoverableAllowanceForCreditLossRecovery	0	USD
	us-gaap	Reinsurance Recoverable Allowance For Credit Loss Recovery ReinsuranceRecoverableAllowanceForCreditLossRecovery	0	USD
	us-gaap	Reinsurance Recoverable Allowance For Credit Loss Recovery ReinsuranceRecoverableAllowanceForCreditLossRecovery	0	USD
CY2021Q3	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1595000	USD
CY2020Q3	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1831000	USD
CY2021Q3	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1595000	USD
CY2020Q3	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1831000	USD
	sigi	Change In Direct Premiums Written ChangeInDirectPremiumsWritten	375900000	USD
	sigi	Change In Direct Premiums Written Percentage ChangeInDirectPremiumsWrittenPercentage	0.16
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
	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	1408240000	USD
	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	1295285000	USD
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	1340293000	USD
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	1252075000	USD
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	430288000	USD
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	421981000	USD
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	675782000	USD
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	646974000	USD
	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	1106070000	USD
	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	1068955000	USD
CY2021Q3	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	3940309000	USD
CY2020Q3	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	3703217000	USD
CY2021Q3	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	670031000	USD
CY2020Q3	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	590059000	USD
CY2021Q3	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	4610340000	USD
CY2020Q3	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	4293276000	USD
	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	4
CY2021Q3	us-gaap	Net Investment Income NetInvestmentIncome	93032000	USD
CY2020Q3	us-gaap	Net Investment Income NetInvestmentIncome	68185000	USD
	us-gaap	Net Investment Income NetInvestmentIncome	246479000	USD
	us-gaap	Net Investment Income NetInvestmentIncome	158596000	USD
CY2021Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	177000	USD
CY2020Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	7721000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	15353000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	-24296000	USD
CY2021Q3	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	93209000	USD
CY2020Q3	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	75906000	USD
	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	261832000	USD
	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	134300000	USD
CY2021Q3	us-gaap	Revenues Revenues	865044000	USD
CY2020Q3	us-gaap	Revenues Revenues	776566000	USD
	us-gaap	Revenues Revenues	2509469000	USD
	us-gaap	Revenues Revenues	2123842000	USD
CY2021Q3	us-gaap	Net Investment Income NetInvestmentIncome	93032000	USD
CY2020Q3	us-gaap	Net Investment Income NetInvestmentIncome	68185000	USD
	us-gaap	Net Investment Income NetInvestmentIncome	246479000	USD
	us-gaap	Net Investment Income NetInvestmentIncome	158596000	USD
CY2021Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	177000	USD
CY2020Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	7721000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	15353000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	-24296000	USD
CY2021Q3	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	93209000	USD
CY2020Q3	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	75906000	USD
	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	261832000	USD
	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	134300000	USD
CY2021Q3	sigi	Taxoninvestmentincome Taxoninvestmentincome	18379000	USD
CY2020Q3	sigi	Taxoninvestmentincome Taxoninvestmentincome	14676000	USD
	sigi	Taxoninvestmentincome Taxoninvestmentincome	51229000	USD
	sigi	Taxoninvestmentincome Taxoninvestmentincome	24338000	USD
CY2021Q3	sigi	Totalinvestmentsegmentincomeafterfederalincometax Totalinvestmentsegmentincomeafterfederalincometax	74830000	USD
CY2020Q3	sigi	Totalinvestmentsegmentincomeafterfederalincometax Totalinvestmentsegmentincomeafterfederalincometax	61230000	USD
	sigi	Totalinvestmentsegmentincomeafterfederalincometax Totalinvestmentsegmentincomeafterfederalincometax	210603000	USD
	sigi	Totalinvestmentsegmentincomeafterfederalincometax Totalinvestmentsegmentincomeafterfederalincometax	109962000	USD
CY2021Q3	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	93209000	USD
CY2020Q3	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	75906000	USD
	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	261832000	USD
	sigi	Total Investmentsrevenue TotalInvestmentsrevenue	134300000	USD
CY2021Q3	us-gaap	Interest Expense Debt InterestExpenseDebt	7242000	USD
CY2020Q3	us-gaap	Interest Expense Debt InterestExpenseDebt	7781000	USD
	us-gaap	Interest Expense Debt InterestExpenseDebt	21967000	USD
	us-gaap	Interest Expense Debt InterestExpenseDebt	23310000	USD
CY2021Q3	us-gaap	Other General Expense OtherGeneralExpense	4270000	USD
CY2020Q3	us-gaap	Other General Expense OtherGeneralExpense	3905000	USD
	us-gaap	Other General Expense OtherGeneralExpense	22936000	USD
	us-gaap	Other General Expense OtherGeneralExpense	19310000	USD
CY2021Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	92636000	USD
CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	85257000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	381466000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	143947000	USD
CY2021Q3	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	2300000	USD
CY2020Q3	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	0	USD
	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	7053000	USD
	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	0	USD
CY2021Q3	sigi	Income Available To Common Stockholders Before Tax IncomeAvailableToCommonStockholdersBeforeTax	90336000	USD
CY2020Q3	sigi	Income Available To Common Stockholders Before Tax IncomeAvailableToCommonStockholdersBeforeTax	85257000	USD
	sigi	Income Available To Common Stockholders Before Tax IncomeAvailableToCommonStockholdersBeforeTax	374413000	USD
	sigi	Income Available To Common Stockholders Before Tax IncomeAvailableToCommonStockholdersBeforeTax	143947000	USD
CY2021Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	92636000	USD
CY2021Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	18931000	USD
CY2021Q3	us-gaap	Net Income Loss NetIncomeLoss	73705000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-35285000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-7410000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-27875000	USD
CY2021Q3	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income Gross NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeGross	-2343000	USD
CY2021Q3	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income Tax NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeTax	-492000	USD
CY2021Q3	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome	-1851000	USD
CY2021Q3	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Before Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax	-1000	USD
CY2021Q3	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax	0	USD
CY2021Q3	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	-1000	USD
CY2021Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securitiesbefore Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesbeforeTax	-1296000	USD
CY2021Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesTax	-272000	USD
CY2021Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	-1024000	USD
CY2021Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Gross DebtSecuritiesAvailableforsaleAllowanceforCreditLossGross	1334000	USD
CY2021Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Tax DebtSecuritiesAvailableforsaleAllowanceforCreditLossTax	280000	USD
CY2021Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	1054000	USD
CY2021Q3	sigi	Total Unrealized Gains Losses On Investment Securities Gross TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross	-37589000	USD
CY2021Q3	sigi	Total Unrealized Gains Losses On Investment Securities Tax TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax	-7894000	USD
CY2021Q3	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	29695000	USD
CY2021Q3	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
CY2021Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-145000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-548000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-693000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-145000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-548000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-36896000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-7749000	USD
CY2021Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-29147000	USD
CY2021Q3	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	55740000	USD
CY2021Q3	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	11182000	USD
CY2021Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	44558000	USD
CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	85257000	USD
CY2020Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	15382000	USD
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	69875000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	37836000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	7947000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	29889000	USD
CY2020Q3	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income Gross NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeGross	9239000	USD
CY2020Q3	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income Tax NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeTax	1940000	USD
CY2020Q3	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome	7299000	USD
CY2020Q3	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Before Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax	1000	USD
CY2020Q3	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax	1000	USD
CY2020Q3	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	0	USD
CY2020Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securitiesbefore Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesbeforeTax	-515000	USD
CY2020Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesTax	-109000	USD
CY2020Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	-406000	USD
CY2020Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Gross DebtSecuritiesAvailableforsaleAllowanceforCreditLossGross	-2853000	USD
CY2020Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Tax DebtSecuritiesAvailableforsaleAllowanceforCreditLossTax	-599000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	381466000	USD
CY2020Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	-2254000	USD
CY2020Q3	sigi	Total Unrealized Gains Losses On Investment Securities Gross TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross	43706000	USD
CY2020Q3	sigi	Total Unrealized Gains Losses On Investment Securities Tax TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax	9178000	USD
CY2020Q3	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	-34528000	USD
CY2020Q3	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
CY2020Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-158000	USD
CY2020Q3	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
CY2020Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-754000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-158000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-596000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	44460000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	9336000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	35124000	USD
CY2020Q3	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	129717000	USD
CY2020Q3	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	24718000	USD
	us-gaap	Net Income Loss NetIncomeLoss	304858000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-103040000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-21638000	USD
CY2020Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	104999000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	76608000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-81402000	USD
	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income Gross NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeGross	-3678000	USD
	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income Tax NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeTax	-772000	USD
	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome	-2906000	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Before Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax	4000	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax	1000	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	3000	USD
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securitiesbefore Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesbeforeTax	-634000	USD
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesTax	-133000	USD
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	-501000	USD
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Gross DebtSecuritiesAvailableforsaleAllowanceforCreditLossGross	4059000	USD
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Tax DebtSecuritiesAvailableforsaleAllowanceforCreditLossTax	852000	USD
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	3207000	USD
	sigi	Total Unrealized Gains Losses On Investment Securities Gross TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross	-103297000	USD
	sigi	Total Unrealized Gains Losses On Investment Securities Tax TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax	-21692000	USD
	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	81605000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-2079000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-436000	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	-1643000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-2079000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-436000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-1643000	USD
	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-101218000	USD
	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-21256000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-79962000	USD
	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	280248000	USD
	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	55352000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	224896000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	143947000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	24653000	USD
	us-gaap	Net Income Loss NetIncomeLoss	119294000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	132623000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	27852000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	104771000	USD
	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income Gross NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeGross	-18672000	USD
	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income Tax NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeTax	-3921000	USD
	sigi	Non Credit Portionof Other Than Temporary Impairments Recognizedin Other Comprehensive Income NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome	-14751000	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Before Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax	7000	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax	2000	USD
	sigi	Amortization Of Net Unrealized Gains Losses On Held To Maturity Transferred From Available For Sale Netof Tax AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax	5000	USD
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securitiesbefore Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesbeforeTax	9126000	USD
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesTax	1916000	USD
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	7210000	USD
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Gross DebtSecuritiesAvailableforsaleAllowanceforCreditLossGross	8010000	USD
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Tax DebtSecuritiesAvailableforsaleAllowanceforCreditLossTax	1682000	USD
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	6328000	USD
	sigi	Total Unrealized Gains Losses On Investment Securities Gross TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross	131080000	USD
	sigi	Total Unrealized Gains Losses On Investment Securities Tax TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax	27527000	USD
	sigi	Total Unrealized Gains Losseson Investment Securities TotalUnrealizedGainsLossesonInvestmentSecurities	-103553000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-2261000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-474000	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	-1787000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-2261000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-474000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-1787000	USD
	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	133341000	USD
	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	28001000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	105340000	USD
	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	277288000	USD
	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	52654000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	224634000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-1643000	USD
CY2020Q4	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	100000000	USD
	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	52781	shares
	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	3400000	USD
CY2021Q3	us-gaap	Stock Repurchase Program Remaining Authorized Repurchase Amount1 StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1	96600000	USD

Files In Submission

Name	View Source	Status
0000230557-21-000033-index-headers.html	Edgar Link	pending
0000230557-21-000033-index.html	Edgar Link	pending
0000230557-21-000033.txt	Edgar Link	pending
0000230557-21-000033-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
R11.htm	Edgar Link	pending
R12.htm	Edgar Link	pending
R13.htm	Edgar Link	pending
R14.htm	Edgar Link	pending
R15.htm	Edgar Link	pending
R16.htm	Edgar Link	pending
R17.htm	Edgar Link	pending
R18.htm	Edgar Link	pending
R19.htm	Edgar Link	pending
R2.htm	Edgar Link	pending
R20.htm	Edgar Link	pending
R21.htm	Edgar Link	pending
R22.htm	Edgar Link	pending
R23.htm	Edgar Link	pending
R24.htm	Edgar Link	pending
R25.htm	Edgar Link	pending
R26.htm	Edgar Link	pending
R27.htm	Edgar Link	pending
R28.htm	Edgar Link	pending
R29.htm	Edgar Link	pending
R3.htm	Edgar Link	pending
R30.htm	Edgar Link	pending
R31.htm	Edgar Link	pending
R32.htm	Edgar Link	pending
R33.htm	Edgar Link	pending
R34.htm	Edgar Link	pending
R35.htm	Edgar Link	pending
R36.htm	Edgar Link	pending
R37.htm	Edgar Link	pending
R38.htm	Edgar Link	pending
R39.htm	Edgar Link	pending
R4.htm	Edgar Link	pending
R40.htm	Edgar Link	pending
R41.htm	Edgar Link	pending
R42.htm	Edgar Link	pending
R43.htm	Edgar Link	pending
R44.htm	Edgar Link	pending
R45.htm	Edgar Link	pending
R46.htm	Edgar Link	pending
R47.htm	Edgar Link	pending
R48.htm	Edgar Link	pending
R49.htm	Edgar Link	pending
R5.htm	Edgar Link	pending
R50.htm	Edgar Link	pending
R51.htm	Edgar Link	pending
R52.htm	Edgar Link	pending
R53.htm	Edgar Link	pending
R54.htm	Edgar Link	pending
R55.htm	Edgar Link	pending
R56.htm	Edgar Link	pending
R57.htm	Edgar Link	pending
R58.htm	Edgar Link	pending
R59.htm	Edgar Link	pending
R6.htm	Edgar Link	pending
R60.htm	Edgar Link	pending
R61.htm	Edgar Link	pending
R7.htm	Edgar Link	pending
R8.htm	Edgar Link	pending
R9.htm	Edgar Link	pending
report.css	Edgar Link	pending
Show.js	Edgar Link	pending
sigi-20210930.htm	Edgar Link	pending
sigi-20210930.xsd	Edgar Link	pending
sigi-20210930_cal.xml	Edgar Link	unprocessable
sigi-20210930_def.xml	Edgar Link	unprocessable
sigi-20210930_htm.xml	Edgar Link	completed
sigi-20210930_lab.xml	Edgar Link	unprocessable
sigi-20210930_pre.xml	Edgar Link	unprocessable
sigi-ex101_9302021xq3.htm	Edgar Link	pending
sigi-ex102_9302021xq3.htm	Edgar Link	pending
sigi-ex103_9302021xq3.htm	Edgar Link	pending
sigi-ex11_9302021xq3.htm	Edgar Link	pending
sigi-ex311_9302021xq3.htm	Edgar Link	pending
sigi-ex312_9302021xq3.htm	Edgar Link	pending
sigi-ex321_9302021xq3.htm	Edgar Link	pending
sigi-ex322_9302021xq3.htm	Edgar Link	pending

Create your account

Find Stocks Worth Researching

Deeply Understand Businesses

Value Businesses Intelligently

$SIGI
Selective Insurance Group Inc Stock $sigi

2021 Q4 Form 10-Q Financial Statement

#000023055721000033 Filed on October 28, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$SIGI Selective Insurance Group Inc Stock $sigi

2021 Q4 Form 10-Q Financial Statement

#000023055721000033 Filed on October 28, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$SIGI
Selective Insurance Group Inc Stock $sigi