$SIGI
Selective Insurance Group Inc Stock $sigi

$sigi Overview Financials Valuation SEC Filings Company Website

2024 Q4 Form 10-Q Financial Statement

#000023055724000026 Filed on October 25, 2024

Income Statement

Concept	2024 Q4	2024 Q3	2023 Q3
Revenue		$1.244B	$1.081B
YoY Change		15.1%	20.79%
Cost Of Revenue		$765.7M	$645.9M
YoY Change		18.54%
Gross Profit		$478.6M	$435.2M
YoY Change		9.99%
Gross Profit Margin		38.47%	40.25%
Selling, General & Admin		$4.700M	$5.900M
YoY Change		-20.34%	6.85%
% of Gross Profit		0.98%	1.36%
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization		$235.6M	$201.1M
YoY Change		17.13%	12.32%
% of Gross Profit		49.21%	46.21%
Operating Expenses		$1.121B	$961.4M
YoY Change		16.55%	15.11%
Operating Profit		-$641.9M	-$526.2M
YoY Change		21.98%
Interest Expense		-$7.300M	-$6.700M
YoY Change		8.96%	-55.2%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income		$116.5M	$112.5M
YoY Change		3.53%	113.75%
Income Tax		$24.21M	$23.31M
% Of Pretax Income		20.78%	20.72%
Net Earnings		$92.28M	$89.21M
YoY Change		3.44%	109.78%
Net Earnings / Revenue		7.42%	8.25%
Basic Earnings Per Share		$1.48	$1.43
Diluted Earnings Per Share		$1.47	$1.42
COMMON SHARES
Basic Shares Outstanding	60.79M shares	60.83M shares	60.57M shares
Diluted Shares Outstanding		61.29M shares	61.02M shares

Balance Sheet

Concept	2024 Q3	2023 Q3
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$12.66M	$13.35M
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	$92.20M	$81.37M
YoY Change	13.3%	-4.64%
Goodwill	$7.849M	$7.849M
YoY Change	0.0%	0.0%
Intangibles
YoY Change
Long-Term Investments	$9.635B	$8.196B
YoY Change	17.56%	8.76%
Other Assets	$113.3M	$213.0M
YoY Change	-46.81%	23.08%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$13.47B	$11.43B
YoY Change	17.9%	8.63%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$113.5M	$114.0M
YoY Change	-0.44%	1.58%
Deferred Revenue
YoY Change
Short-Term Debt	$0.00	$0.00
YoY Change
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$113.5M	$117.0M
YoY Change	-2.99%	4.25%
LONG-TERM LIABILITIES
Long-Term Debt	$508.2M	$505.0M
YoY Change	0.63%	-0.03%
Other Long-Term Liabilities	$576.6M	$519.0M
YoY Change	11.1%	6.34%
Total Long-Term Liabilities	$1.085B	$1.024B
YoY Change	5.94%	3.1%
TOTAL LIABILITIES
Total Short-Term Liabilities	$113.5M	$117.0M
Total Long-Term Liabilities	$1.085B	$1.024B
Total Liabilities	$10.31B	$8.784B
YoY Change	17.33%	8.53%
SHAREHOLDERS EQUITY
Retained Earnings	$3.070B	$2.928B
YoY Change	4.83%	9.11%
Common Stock	$760.9M	$727.2M
YoY Change	4.63%	4.51%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$650.7M	$635.1M
YoY Change	2.47%	1.29%
Treasury Stock Shares
Shareholders Equity	$3.168B	$2.644B
YoY Change
Total Liabilities & Shareholders Equity	$13.47B	$11.43B
YoY Change	17.9%	8.63%

Cashflow Statement

Concept	2024 Q3	2023 Q3
OPERATING ACTIVITIES
Net Income	$92.28M	$89.21M
YoY Change	3.44%	109.78%
Depreciation, Depletion And Amortization	$235.6M	$201.1M
YoY Change	17.13%	12.32%
Cash From Operating Activities	$387.4M	$228.7M
YoY Change	69.38%	-5.48%
INVESTING ACTIVITIES
Capital Expenditures	$9.405M	$5.300M
YoY Change	77.45%	-169.22%
Acquisitions
YoY Change
Other Investing Activities	-$344.6M	-$211.3M
YoY Change	63.09%	1.24%
Cash From Investing Activities	-$354.0M	-$216.4M
YoY Change	63.6%	0.01%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-31.59M	-20.10M
YoY Change	57.16%	-16.68%
NET CHANGE
Cash From Operating Activities	387.4M	228.7M
Cash From Investing Activities	-354.0M	-216.4M
Cash From Financing Activities	-31.59M	-20.10M
Net Change In Cash	1.756M	-7.800M
YoY Change	-122.51%	-631.7%
FREE CASH FLOW
Cash From Operating Activities	$387.4M	$228.7M
Capital Expenditures	$9.405M	$5.300M
Free Cash Flow	$378.0M	$223.4M
YoY Change	69.19%	-10.5%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
	dei	Document Type DocumentType	10-Q
	dei	Document Transition Report DocumentTransitionReport	false
	dei	Amendment Flag AmendmentFlag	false
	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2024
	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 Quarterly Report DocumentQuarterlyReport	true
	dei	Document Period End Date DocumentPeriodEndDate	2024-09-30
	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
	dei	Entity Small Business EntitySmallBusiness	false
CY2024Q3	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	21440000	usd
CY2024Q3	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	0	usd
CY2023Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	0	usd
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CY2024Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	28504000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	28212000	usd
CY2024Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	8269338000	usd
CY2023Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	7880697000	usd
CY2024Q3	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	8088601000	usd
CY2023Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	7499197000	usd
CY2024Q3	sigi	Commercialmortgageloanfairvalue Commercialmortgageloanfairvalue	218599000	usd
CY2024Q3	us-gaap	Other Investments OtherInvestments	102496000	usd
CY2023Q4	us-gaap	Accrued Investment Income Receivable AccruedInvestmentIncomeReceivable	66339000	usd
CY2024Q3	us-gaap	Premiums Receivable Gross PremiumsReceivableGross	1552740000	usd
CY2023Q4	us-gaap	Premiums Receivable Gross PremiumsReceivableGross	1331979000	usd
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CY2023Q4	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	18900000	usd
CY2024Q3	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	1531940000	usd
CY2023Q4	us-gaap	Premiums Receivable At Carrying Value PremiumsReceivableAtCarryingValue	1313079000	usd
CY2024Q3	us-gaap	Reinsurance Recoverables On Unpaid Losses Gross ReinsuranceRecoverablesOnUnpaidLossesGross	1059251000	usd
CY2023Q4	us-gaap	Reinsurance Recoverables On Paid And Unpaid Losses ReinsuranceRecoverablesOnPaidAndUnpaidLosses	656825000	usd
CY2024Q3	us-gaap	Prepaid Reinsurance Premiums PrepaidReinsurancePremiums	230705000	usd
CY2023Q4	us-gaap	Prepaid Reinsurance Premiums PrepaidReinsurancePremiums	203320000	usd
CY2024Q3	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	100716000	usd
CY2023Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	140237000	usd
CY2024Q3	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	285067000	usd
CY2023Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	271409000	usd
CY2024Q3	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	92195000	usd
CY2023Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	83272000	usd
CY2024Q3	us-gaap	Deferred Policy Acquisition Costs DeferredPolicyAcquisitionCosts	488521000	usd
CY2023Q4	us-gaap	Deferred Policy Acquisition Costs DeferredPolicyAcquisitionCosts	424864000	usd
CY2024Q3	us-gaap	Goodwill Goodwill	7849000	usd
CY2023Q4	us-gaap	Goodwill Goodwill	7849000	usd
CY2024Q3	us-gaap	Other Assets OtherAssets	229130000	usd
CY2023Q4	us-gaap	Other Assets OtherAssets	199760000	usd
CY2024Q3	us-gaap	Assets Assets	13473137000	usd
CY2023Q4	us-gaap	Assets Assets	11802546000	usd
CY2024Q3	us-gaap	Unearned Premiums UnearnedPremiums	2655000000	usd
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CY2024Q3	us-gaap	Long Term Debt And Capital Lease Obligations Including Current Maturities LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities	508237000	usd
CY2023Q4	us-gaap	Long Term Debt And Capital Lease Obligations Including Current Maturities LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities	503946000	usd
CY2024Q3	us-gaap	Accrued Income Taxes AccruedIncomeTaxes	0	usd
CY2023Q4	us-gaap	Accrued Income Taxes AccruedIncomeTaxes	6251000	usd
CY2024Q3	us-gaap	Employee Related Liabilities Current And Noncurrent EmployeeRelatedLiabilitiesCurrentAndNoncurrent	113475000	usd
CY2023Q4	us-gaap	Employee Related Liabilities Current And Noncurrent EmployeeRelatedLiabilitiesCurrentAndNoncurrent	122003000	usd
	us-gaap	Other Income OtherIncome	22566000	usd
	us-gaap	Other Income OtherIncome	13919000	usd
	us-gaap	Revenues Revenues	3605270000	usd
	us-gaap	Revenues Revenues	3121425000	usd
	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	681421000	usd
	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	585660000	usd
	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	338449000	usd
	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	325949000	usd
	us-gaap	Interest Expense Debt InterestExpenseDebt	21633000	usd
	us-gaap	Interest Expense Debt InterestExpenseDebt	21610000	usd
	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	29314000	usd
	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	27308000	usd
	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	3466315000	usd
	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	2819992000	usd
	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-3455000	usd
	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-5961000	usd
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	27478000	usd
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	61043000	usd
	us-gaap	Net Income Loss NetIncomeLoss	111477000	usd
	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	6900000	usd
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	104577000	usd
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	233490000	usd
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.72
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.85
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.71
CY2023Q4	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	18900000	usd
CY2022Q4	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	16100000	usd
CY2023Q2	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1800000	usd
CY2023Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1700000	usd
CY2022Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1600000	usd
CY2023Q4	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	618601000	usd
CY2023Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.42
CY2023Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	86908000	usd
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	104577000	usd
CY2023Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	60676000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	60867000	shares
CY2024Q3	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	414000	shares
CY2023Q3	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	340000	shares
	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	392000	shares
CY2024Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	61291000	shares
CY2023Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	61016000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	61259000	shares
CY2024Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.48
CY2023Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.43
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.72
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CY2024Q3	us-gaap	Cash Cash	98000	usd
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CY2023Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0
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	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	3243403000	usd
	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	2826403000	usd
	us-gaap	Net Investment Income NetInvestmentIncome	334250000	usd
	us-gaap	Net Investment Income NetInvestmentIncome	290065000	usd
	us-gaap	Gain Loss On Investments GainLossOnInvestments	5051000	usd
	us-gaap	Gain Loss On Investments GainLossOnInvestments	-8962000	usd
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	138955000	usd
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	301433000	usd
	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	30933000	usd
	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	67004000	usd
	us-gaap	Net Income Loss NetIncomeLoss	240390000	usd
	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Net UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsNet	-13032000	usd
CY2024Q3	us-gaap	Interest Expense Debt InterestExpenseDebt	7250000	usd
	dei	Entity Shell Company EntityShellCompany	false
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	dei	Entity Registrant Name EntityRegistrantName	SELECTIVE INSURANCE GROUP, INC
	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	22-2168890
	dei	Entity Address Address Line1 EntityAddressAddressLine1	40 Wantage Avenue
	dei	Entity Address City Or Town EntityAddressCityOrTown	Branchville
	dei	Entity Address State Or Province EntityAddressStateOrProvince	NJ
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CY2023Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	8000	shares
CY2024Q3	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	8000	shares
CY2023Q4	us-gaap	Preferred Stock Liquidation Preference PreferredStockLiquidationPreference	25000
CY2024Q3	us-gaap	Preferred Stock Liquidation Preference PreferredStockLiquidationPreference	25000
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CY2024Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-211875000	usd
CY2024Q3	us-gaap	Treasury Stock Common Shares TreasuryStockCommonShares	44760620	shares
CY2024Q3	us-gaap	Treasury Stock Value TreasuryStockValue	650748000	usd
CY2024Q3	us-gaap	Net Investment Income NetInvestmentIncome	117759000	usd
CY2023Q3	us-gaap	Net Investment Income NetInvestmentIncome	100863000	usd
CY2024Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	5389000	usd
CY2023Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	-6880000	usd
CY2024Q3	us-gaap	Other Income OtherIncome	8930000	usd
CY2023Q3	us-gaap	Other Income OtherIncome	5181000	usd
CY2023Q3	us-gaap	Revenues Revenues	1081081000	usd
CY2024Q3	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	235560000	usd
CY2023Q3	us-gaap	Deferred Policy Acquisition Cost Amortization Expense DeferredPolicyAcquisitionCostAmortizationExpense	201106000	usd
CY2024Q3	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	114689000	usd
CY2023Q3	us-gaap	Other Underwriting Expense OtherUnderwritingExpense	108504000	usd
CY2023Q3	us-gaap	Interest Expense Debt InterestExpenseDebt	7186000	usd
CY2024Q3	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	4662000	usd
CY2023Q3	us-gaap	Operating Costs And Expenses OperatingCostsAndExpenses	5871000	usd
CY2024Q3	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	1127819000	usd
CY2023Q3	us-gaap	Benefits Losses And Expenses BenefitsLossesAndExpenses	968564000	usd
CY2024Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	116487000	usd
CY2023Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	112517000	usd
CY2024Q3	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	27142000	usd
CY2023Q3	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	24133000	usd
CY2024Q3	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-2933000	usd
CY2023Q3	us-gaap	Net Income Loss NetIncomeLoss	89208000	usd
CY2024Q3	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	2300000	usd
CY2023Q3	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	2300000	usd
	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	6900000	usd
CY2024Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	89978000	usd
CY2023Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	86908000	usd
CY2024Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.48
CY2023Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.43
CY2024Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.47
CY2023Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.42
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.83
CY2024Q3	us-gaap	Net Income Loss NetIncomeLoss	92278000	usd
	us-gaap	Net Income Loss NetIncomeLoss	111477000	usd
	us-gaap	Net Income Loss NetIncomeLoss	240390000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	148098000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-80361000	usd
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	129211000	usd
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-76219000	usd
CY2024Q3	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Net UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsNet	34702000	usd
CY2023Q3	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Net UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsNet	-25989000	usd
	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Net UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsNet	29301000	usd
CY2024Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	-986000	usd
CY2023Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	3656000	usd
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	-1014000	usd
CY2023Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	1949000	usd
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	-6261000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	180082000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-100745000	usd
	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	158834000	usd
	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-79621000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-764000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-598000	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	-2292000	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	-1794000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-764000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-598000	usd
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-2292000	usd
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-1794000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	180846000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-100147000	usd
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	161126000	usd
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-77827000	usd
CY2024Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	273124000	usd
CY2023Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-10939000	usd
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	272603000	usd
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	162563000	usd
	dei	Entity File Number EntityFileNumber	001-33067
	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	NJ
	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	07890
	dei	City Area Code CityAreaCode	(973)
	dei	Local Phone Number LocalPhoneNumber	948-3000
	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2023Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	21923000	usd
CY2023Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	187155000	usd
CY2024Q3	us-gaap	Other Short Term Investments OtherShortTermInvestments	561032000	usd
CY2023Q4	us-gaap	Other Short Term Investments OtherShortTermInvestments	309317000	usd
CY2024Q3	us-gaap	Alternative Investment AlternativeInvestment	431999000	usd
CY2023Q4	us-gaap	Alternative Investment AlternativeInvestment	395779000	usd
CY2023Q4	us-gaap	Cash Cash	180000	usd
CY2024Q3	us-gaap	Restricted Cash RestrictedCash	12566000	usd
CY2024Q3	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	6451996000	usd
CY2023Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	5336911000	usd
CY2024Q3	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	105553451	shares
CY2023Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	105223307	shares
CY2024Q3	us-gaap	Common Stock Value CommonStockValue	211107000	usd
CY2023Q4	us-gaap	Common Stock Value CommonStockValue	210447000	usd
CY2023Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	522748000	usd
CY2023Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-373001000	usd
CY2023Q4	us-gaap	Treasury Stock Common Shares TreasuryStockCommonShares	44586870	shares
CY2023Q4	us-gaap	Treasury Stock Value TreasuryStockValue	635209000	usd
CY2024Q3	us-gaap	Stockholders Equity StockholdersEquity	3167801000	usd
CY2023Q4	us-gaap	Stockholders Equity StockholdersEquity	2954381000	usd
CY2024Q3	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		usd
CY2023Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		usd
CY2024Q3	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	13473137000	usd
CY2023Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	11802546000	usd
CY2024Q3	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	1112228000	usd
CY2023Q3	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	981917000	usd
CY2024Q3	us-gaap	Revenues Revenues	1244306000	usd
CY2024Q3	us-gaap	Policyholder Benefits And Claims Incurred Net PolicyholderBenefitsAndClaimsIncurredNet	765658000	usd
CY2023Q3	us-gaap	Policyholder Benefits And Claims Incurred Net PolicyholderBenefitsAndClaimsIncurredNet	645897000	usd
	us-gaap	Policyholder Benefits And Claims Incurred Net PolicyholderBenefitsAndClaimsIncurredNet	2395498000	usd
	us-gaap	Policyholder Benefits And Claims Incurred Net PolicyholderBenefitsAndClaimsIncurredNet	1859465000	usd
CY2023Q3	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-824000	usd
CY2024Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	24209000	usd
CY2023Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	23309000	usd
CY2024Q3	us-gaap	Net Income Loss NetIncomeLoss	92278000	usd
CY2023Q3	us-gaap	Net Income Loss NetIncomeLoss	89208000	usd
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	15891000	usd
CY2024Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	-1732000	usd
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	1336000	usd
CY2024Q3	us-gaap	Stockholders Equity StockholdersEquity	3167801000	usd
CY2023Q3	us-gaap	Stockholders Equity StockholdersEquity	2644423000	usd
CY2024Q3	us-gaap	Stockholders Equity StockholdersEquity	3167801000	usd
CY2023Q3	us-gaap	Stockholders Equity StockholdersEquity	2644423000	usd
CY2024Q3	us-gaap	Preferred Stock Dividends Per Share Declared PreferredStockDividendsPerShareDeclared	287.50
CY2023Q3	us-gaap	Preferred Stock Dividends Per Share Declared PreferredStockDividendsPerShareDeclared	287.50
	us-gaap	Preferred Stock Dividends Per Share Declared PreferredStockDividendsPerShareDeclared	862.50
	us-gaap	Preferred Stock Dividends Per Share Declared PreferredStockDividendsPerShareDeclared	862.50
CY2024Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.35
CY2023Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.30
	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.05
	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.90
	us-gaap	Net Income Loss NetIncomeLoss	111477000	usd
	us-gaap	Net Income Loss NetIncomeLoss	240390000	usd
	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	27228000	usd
	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	23432000	usd
	us-gaap	Share Based Compensation ShareBasedCompensation	19797000	usd
	us-gaap	Share Based Compensation ShareBasedCompensation	16374000	usd
	us-gaap	Income Loss From Equity Method Investments Net Of Dividends Or Distributions IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions	18573000	usd
	us-gaap	Income Loss From Equity Method Investments Net Of Dividends Or Distributions IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions	16266000	usd
	sigi	Proceedsfromequityinvestmentsinexcessofcurrentyearearnings Proceedsfromequityinvestmentsinexcessofcurrentyearearnings	15395000	usd
	sigi	Proceedsfromequityinvestmentsinexcessofcurrentyearearnings Proceedsfromequityinvestmentsinexcessofcurrentyearearnings	8656000	usd
	us-gaap	Gain Loss On Investments GainLossOnInvestments	5051000	usd
	us-gaap	Gain Loss On Investments GainLossOnInvestments	-8962000	usd
	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	-321000	usd
	us-gaap	Gain Loss On Sale Of Property Plant Equipment GainLossOnSaleOfPropertyPlantEquipment	6000	usd
	sigi	Increase Decrease In Reserves For Losses And Loss Expenses Net Of Reinsurance Recoverables IncreaseDecreaseInReservesForLossesAndLossExpensesNetOfReinsuranceRecoverables	714659000	usd
	sigi	Increase Decrease In Reserves For Losses And Loss Expenses Net Of Reinsurance Recoverables IncreaseDecreaseInReservesForLossesAndLossExpensesNetOfReinsuranceRecoverables	254018000	usd
	sigi	Increase Decrease In Unearned Premiums Net Of Prepaid Reinsurance IncreaseDecreaseInUnearnedPremiumsNetOfPrepaidReinsurance	296959000	usd
	sigi	Increase Decrease In Unearned Premiums Net Of Prepaid Reinsurance IncreaseDecreaseInUnearnedPremiumsNetOfPrepaidReinsurance	316597000	usd
	us-gaap	Increase Decrease In Income Taxes IncreaseDecreaseInIncomeTaxes	-22597000	usd
	us-gaap	Increase Decrease In Income Taxes IncreaseDecreaseInIncomeTaxes	216000	usd
	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	218861000	usd
	us-gaap	Increase Decrease In Premiums Receivable IncreaseDecreaseInPremiumsReceivable	244361000	usd
	us-gaap	Increase Decrease In Deferred Policy Acquisition Costs IncreaseDecreaseInDeferredPolicyAcquisitionCosts	63657000	usd
	us-gaap	Increase Decrease In Deferred Policy Acquisition Costs IncreaseDecreaseInDeferredPolicyAcquisitionCosts	57130000	usd
	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	7427000	usd
	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	3038000	usd
	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	-8528000	usd
	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	-946000	usd
	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	33138000	usd
	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	12496000	usd
	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-40301000	usd
	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-12096000	usd
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	767703000	usd
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	522306000	usd
	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	2700000	usd
	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	0	usd
	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	1767201000	usd
	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	1999665000	usd
	us-gaap	Payments To Acquire Mortgage Notes Receivable PaymentsToAcquireMortgageNotesReceivable	46122000	usd
	us-gaap	Payments To Acquire Mortgage Notes Receivable PaymentsToAcquireMortgageNotesReceivable	38281000	usd
	us-gaap	Payments To Acquire Equity Securities Fv Ni PaymentsToAcquireEquitySecuritiesFvNi	25603000	usd
	us-gaap	Payments To Acquire Equity Securities Fv Ni PaymentsToAcquireEquitySecuritiesFvNi	13731000	usd
	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	66372000	usd
	us-gaap	Payments To Acquire Other Investments PaymentsToAcquireOtherInvestments	83810000	usd
	us-gaap	Payments To Acquire Short Term Investments PaymentsToAcquireShortTermInvestments	6829793000	usd
	us-gaap	Payments To Acquire Short Term Investments PaymentsToAcquireShortTermInvestments	3483923000	usd
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	743539000	usd
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	1115260000	usd
	us-gaap	Proceeds From Sale And Collection Of Mortgage Notes Receivable ProceedsFromSaleAndCollectionOfMortgageNotesReceivable	11112000	usd
	us-gaap	Proceeds From Sale And Collection Of Mortgage Notes Receivable ProceedsFromSaleAndCollectionOfMortgageNotesReceivable	1473000	usd
	us-gaap	Proceeds From Sale Of Short Term Investments ProceedsFromSaleOfShortTermInvestments	6578742000	usd
	us-gaap	Proceeds From Sale Of Short Term Investments ProceedsFromSaleOfShortTermInvestments	3609991000	usd
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	3441000	usd
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	7918000	usd
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	707322000	usd
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	367495000	usd
	us-gaap	Proceeds From Sale Of Equity Securities Fv Ni ProceedsFromSaleOfEquitySecuritiesFvNi	12252000	usd
	us-gaap	Proceeds From Sale Of Equity Securities Fv Ni ProceedsFromSaleOfEquitySecuritiesFvNi	53344000	usd
	sigi	Proceeds From Sale Of Other Investments Net ProceedsFromSaleOfOtherInvestmentsNet	-4000	usd
	us-gaap	Proceeds From Sale Of Equity Method Investments ProceedsFromSaleOfEquityMethodInvestments	900000	usd
	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	17423000	usd
	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	7765000	usd
	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	23337000	usd
	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	14763000	usd
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-687301000	usd
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-470027000	usd
	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	6900000	usd
	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	6900000	usd
	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	62358000	usd
	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	53122000	usd
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	15539000	usd
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	7804000	usd
	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	5724000	usd
	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions	5616000	usd
	us-gaap	Proceeds From Debt Net Of Issuance Costs ProceedsFromDebtNetOfIssuanceCosts	0	usd
	us-gaap	Proceeds From Debt Net Of Issuance Costs ProceedsFromDebtNetOfIssuanceCosts	20000000	usd
	us-gaap	Repayments Of Debt RepaymentsOfDebt	0	usd
	us-gaap	Repayments Of Debt RepaymentsOfDebt	20000000	usd
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	1937000	usd
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	1933000	usd
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-81010000	usd
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-64143000	usd
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect	-608000	usd
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect	-11864000	usd
CY2023Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	13272000	usd
CY2022Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	25209000	usd
CY2024Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	12664000	usd
CY2023Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	13345000	usd
	us-gaap	Interest Paid Net InterestPaidNet	22823000	usd
	us-gaap	Interest Paid Net InterestPaidNet	22712000	usd
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	46000000	usd
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	57000000	usd
	us-gaap	Operating Lease Payments OperatingLeasePayments	5915000	usd
	us-gaap	Operating Lease Payments OperatingLeasePayments	5773000	usd
	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	152000	usd
	us-gaap	Finance Lease Interest Payment On Liability FinanceLeaseInterestPaymentOnLiability	41000	usd
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	1937000	usd
	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	1933000	usd
	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	5969000	usd
	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	1584000	usd
	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	11513000	usd
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CY2024Q3	us-gaap	Cash Cash	98000	usd
CY2023Q4	us-gaap	Cash Cash	180000	usd
CY2024Q3	us-gaap	Restricted Cash RestrictedCash	12566000	usd
CY2023Q4	us-gaap	Restricted Cash RestrictedCash	13092000	usd
CY2024Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	12664000	usd
CY2023Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	13272000	usd
CY2024Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	8269338000	usd
CY2024Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	28504000	usd
CY2024Q3	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	107715000	usd
CY2024Q3	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	259948000	usd
CY2024Q3	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	8088601000	usd
CY2023Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	7880697000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	28212000	usd
CY2023Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	50076000	usd
CY2023Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	403364000	usd
CY2023Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	7499197000	usd
CY2024Q2	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	31309000	usd
CY2024Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not Previously Recorded DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded	2429000	usd
CY2024Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Purchased With Credit Deterioration Increase DebtSecuritiesAvailableForSaleAllowanceForCreditLossPurchasedWithCreditDeteriorationIncrease	0	usd
CY2024Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not To Sell Before Recovery Credit Loss Previously Recorded Expense Reversal DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal	-4620000	usd
CY2024Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Securities Sold DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold	614000	usd
CY2024Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Sell Before Recovery DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery	0	usd
CY2024Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	28504000	usd
CY2023Q2	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	31425000	usd
CY2023Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not Previously Recorded DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded	2206000	usd
CY2023Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Purchased With Credit Deterioration Increase DebtSecuritiesAvailableForSaleAllowanceForCreditLossPurchasedWithCreditDeteriorationIncrease	0	usd
CY2023Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not To Sell Before Recovery Credit Loss Previously Recorded Expense Reversal DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal	262000	usd
CY2023Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Securities Sold DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold	355000	usd
CY2023Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Sell Before Recovery DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery	0	usd
CY2023Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	33538000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	28212000	usd
	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not Previously Recorded DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded	3329000	usd
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	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not To Sell Before Recovery Credit Loss Previously Recorded Expense Reversal DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal	-1637000	usd
	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Securities Sold DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold	1391000	usd
	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Sell Before Recovery DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery	9000	usd
CY2024Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	28504000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	45721000	usd
	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not Previously Recorded DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded	7107000	usd
	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Purchased With Credit Deterioration Increase DebtSecuritiesAvailableForSaleAllowanceForCreditLossPurchasedWithCreditDeteriorationIncrease	0	usd
	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Not To Sell Before Recovery Credit Loss Previously Recorded Expense Reversal DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal	-15032000	usd
	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Securities Sold DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold	4207000	usd
	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss Sell Before Recovery DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery	51000	usd
CY2023Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	33538000	usd
CY2024Q3	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	623583000	usd
CY2024Q3	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	820000	usd
CY2024Q3	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	833000	usd
CY2024Q3	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	3638555000	usd
CY2024Q3	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	13971000	usd
CY2024Q3	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	13574000	usd
CY2024Q3	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	3030532000	usd
CY2024Q3	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	7167000	usd
CY2024Q3	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	7033000	usd
CY2024Q3	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	795931000	usd
CY2024Q3	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	0	usd
CY2024Q3	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	0	usd
CY2024Q3	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	8088601000	usd
CY2024Q3	us-gaap	Debt Securities Held To Maturity Amortized Cost After Allowance For Credit Loss DebtSecuritiesHeldToMaturityAmortizedCostAfterAllowanceForCreditLoss	21958000	usd
CY2024Q3	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	21440000	usd
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CY2024Q3	us-gaap	Net Investment Income NetInvestmentIncome	117759000	usd
CY2023Q3	us-gaap	Net Investment Income NetInvestmentIncome	100863000	usd
	us-gaap	Net Investment Income NetInvestmentIncome	334250000	usd
	us-gaap	Net Investment Income NetInvestmentIncome	290065000	usd
CY2024Q3	sigi	Debt And Equity Securities Realized Gains DebtAndEquitySecuritiesRealizedGains	4159000	usd
CY2023Q3	sigi	Debt And Equity Securities Realized Gains DebtAndEquitySecuritiesRealizedGains	367000	usd
	sigi	Debt And Equity Securities Realized Gains DebtAndEquitySecuritiesRealizedGains	10681000	usd
	sigi	Debt And Equity Securities Realized Gains DebtAndEquitySecuritiesRealizedGains	5307000	usd
CY2024Q3	sigi	Debt And Equity Securities Realized Losses DebtAndEquitySecuritiesRealizedLosses	2012000	usd
CY2023Q3	sigi	Debt And Equity Securities Realized Losses DebtAndEquitySecuritiesRealizedLosses	5264000	usd
	sigi	Debt And Equity Securities Realized Losses DebtAndEquitySecuritiesRealizedLosses	5228000	usd
	sigi	Debt And Equity Securities Realized Losses DebtAndEquitySecuritiesRealizedLosses	30146000	usd
CY2024Q3	us-gaap	Debt And Equity Securities Realized Gain Loss DebtAndEquitySecuritiesRealizedGainLoss	2147000	usd
CY2023Q3	us-gaap	Debt And Equity Securities Realized Gain Loss DebtAndEquitySecuritiesRealizedGainLoss	-4897000	usd
	us-gaap	Debt And Equity Securities Realized Gain Loss DebtAndEquitySecuritiesRealizedGainLoss	5453000	usd
	us-gaap	Debt And Equity Securities Realized Gain Loss DebtAndEquitySecuritiesRealizedGainLoss	-24839000	usd
CY2024Q3	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	2407000	usd
CY2023Q3	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	489000	usd
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	3006000	usd
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	8662000	usd
CY2024Q3	sigi	Losses On Investment Securities For Which We Have The Intent To Sell LossesOnInvestmentSecuritiesForWhichWeHaveTheIntentToSell	752000	usd
CY2023Q3	sigi	Losses On Investment Securities For Which We Have The Intent To Sell LossesOnInvestmentSecuritiesForWhichWeHaveTheIntentToSell	0	usd
	sigi	Losses On Investment Securities For Which We Have The Intent To Sell LossesOnInvestmentSecuritiesForWhichWeHaveTheIntentToSell	1248000	usd
	sigi	Losses On Investment Securities For Which We Have The Intent To Sell LossesOnInvestmentSecuritiesForWhichWeHaveTheIntentToSell	645000	usd
CY2024Q3	sigi	Other Realized Gains Losses On Investments OtherRealizedGainsLossesOnInvestments	-602000	usd
CY2023Q3	sigi	Other Realized Gains Losses On Investments OtherRealizedGainsLossesOnInvestments	0	usd
	sigi	Other Realized Gains Losses On Investments OtherRealizedGainsLossesOnInvestments	-602000	usd
	sigi	Other Realized Gains Losses On Investments OtherRealizedGainsLossesOnInvestments	0	usd
CY2024Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	5389000	usd
CY2023Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	-6880000	usd
	us-gaap	Gain Loss On Investments GainLossOnInvestments	5051000	usd
	us-gaap	Gain Loss On Investments GainLossOnInvestments	-8962000	usd
CY2024Q3	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	1997000	usd
CY2023Q3	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	200000	usd
	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	4904000	usd
	us-gaap	Unrealized Gain Loss On Investments UnrealizedGainLossOnInvestments	2744000	usd
CY2024Q3	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	410000	usd
CY2023Q3	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	289000	usd
	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	-1898000	usd
	sigi	Unrealized Gain Losson Equity Securities Sold UnrealizedGainLossonEquitySecuritiesSold	5918000	usd
CY2024Q3	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	2407000	usd
CY2023Q3	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	489000	usd
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	3006000	usd
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	8662000	usd
CY2024Q3	us-gaap	Finance Lease Liability FinanceLeaseLiability	6668000	usd
CY2023Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	2636000	usd
CY2024Q3	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	508237000	usd
CY2023Q4	us-gaap	Long Term Debt And Capital Lease Obligations LongTermDebtAndCapitalLeaseObligations	503946000	usd
CY2024Q3	us-gaap	Other Assets Fair Value Disclosure OtherAssetsFairValueDisclosure	213042000	usd
CY2024Q3	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	566725000	usd
CY2023Q4	us-gaap	Other Assets Fair Value Disclosure OtherAssetsFairValueDisclosure	288955000	usd
CY2023Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue	551689000	usd
CY2024Q3	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	21440000	usd
CY2024Q3	sigi	Commercialmortgageloanfairvalue Commercialmortgageloanfairvalue	218599000	usd
CY2024Q3	us-gaap	Long Term Debt Fair Value LongTermDebtFairValue	517310000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	21923000	usd
CY2023Q4	sigi	Commercialmortgageloanfairvalue Commercialmortgageloanfairvalue	178913000	usd
CY2023Q4	us-gaap	Long Term Debt Fair Value LongTermDebtFairValue	503805000	usd
CY2024Q2	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	21100000	usd
CY2023Q2	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	17900000	usd
CY2024Q3	us-gaap	Premium Receivable Credit Loss Expense Reversal PremiumReceivableCreditLossExpenseReversal	1970000	usd
CY2023Q3	us-gaap	Premium Receivable Credit Loss Expense Reversal PremiumReceivableCreditLossExpenseReversal	1973000	usd
	us-gaap	Premium Receivable Credit Loss Expense Reversal PremiumReceivableCreditLossExpenseReversal	6242000	usd
	us-gaap	Premium Receivable Credit Loss Expense Reversal PremiumReceivableCreditLossExpenseReversal	5398000	usd
CY2024Q3	us-gaap	Premiums Receivable Allowance For Doubtful Accounts Write Offs Against Allowance PremiumsReceivableAllowanceForDoubtfulAccountsWriteOffsAgainstAllowance	2764000	usd
CY2023Q3	us-gaap	Premiums Receivable Allowance For Doubtful Accounts Write Offs Against Allowance PremiumsReceivableAllowanceForDoubtfulAccountsWriteOffsAgainstAllowance	1257000	usd
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CY2024Q3	us-gaap	Premiums Receivable Allowance For Doubtful Accounts Recoveries PremiumsReceivableAllowanceForDoubtfulAccountsRecoveries	494000	usd
CY2023Q3	us-gaap	Premiums Receivable Allowance For Doubtful Accounts Recoveries PremiumsReceivableAllowanceForDoubtfulAccountsRecoveries	284000	usd
	us-gaap	Premiums Receivable Allowance For Doubtful Accounts Recoveries PremiumsReceivableAllowanceForDoubtfulAccountsRecoveries	1198000	usd
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CY2024Q3	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	20800000	usd
CY2023Q3	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	18900000	usd
CY2024Q3	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	20800000	usd
CY2023Q3	us-gaap	Premiums Receivable Allowance For Doubtful Accounts PremiumsReceivableAllowanceForDoubtfulAccounts	18900000	usd
CY2024Q3	us-gaap	Reinsurance Recoverables On Unpaid Losses Gross ReinsuranceRecoverablesOnUnpaidLossesGross	1059251000	usd
CY2024Q3	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	2000000	usd
CY2024Q3	us-gaap	Reinsurance Recoverables On Paid And Unpaid Losses ReinsuranceRecoverablesOnPaidAndUnpaidLosses	1057251000	usd
CY2023Q4	us-gaap	Reinsurance Recoverables On Unpaid Losses Gross ReinsuranceRecoverablesOnUnpaidLossesGross	658525000	usd
CY2023Q4	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1700000	usd
CY2023Q4	us-gaap	Reinsurance Recoverables On Paid And Unpaid Losses ReinsuranceRecoverablesOnPaidAndUnpaidLosses	656825000	usd
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CY2024Q2	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1700000	usd
CY2024Q3	us-gaap	Reinsurance Recoverable Credit Loss Expense Reversal ReinsuranceRecoverableCreditLossExpenseReversal	300000	usd
CY2023Q3	us-gaap	Reinsurance Recoverable Credit Loss Expense Reversal ReinsuranceRecoverableCreditLossExpenseReversal	0	usd
	us-gaap	Reinsurance Recoverable Credit Loss Expense Reversal ReinsuranceRecoverableCreditLossExpenseReversal	300000	usd
	us-gaap	Reinsurance Recoverable Credit Loss Expense Reversal ReinsuranceRecoverableCreditLossExpenseReversal	200000	usd
CY2024Q3	us-gaap	Reinsurance Loss On Uncollectible Accounts In Period Amount ReinsuranceLossOnUncollectibleAccountsInPeriodAmount	0	usd
CY2023Q3	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
CY2024Q3	us-gaap	Reinsurance Recoverable Allowance For Credit Loss Recovery ReinsuranceRecoverableAllowanceForCreditLossRecovery	0	usd
CY2023Q3	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
CY2024Q3	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	2000000	usd
CY2023Q3	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1800000	usd
CY2024Q3	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	2000000	usd
CY2023Q3	us-gaap	Reinsurance Recoverables Allowance ReinsuranceRecoverablesAllowance	1800000	usd
CY2024Q3	us-gaap	Direct Premiums Written DirectPremiumsWritten	1335475000	usd
CY2023Q3	us-gaap	Direct Premiums Written DirectPremiumsWritten	1214444000	usd
	us-gaap	Direct Premiums Written DirectPremiumsWritten	4051124000	usd
	us-gaap	Direct Premiums Written DirectPremiumsWritten	3579700000	usd
CY2024Q3	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	7611000	usd
CY2023Q3	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	9087000	usd
	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	20009000	usd
	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	20058000	usd
CY2024Q3	us-gaap	Ceded Premiums Written CededPremiumsWritten	185446000	usd
CY2023Q3	us-gaap	Ceded Premiums Written CededPremiumsWritten	165206000	usd
	us-gaap	Ceded Premiums Written CededPremiumsWritten	530771000	usd
	us-gaap	Ceded Premiums Written CededPremiumsWritten	456758000	usd
CY2024Q3	us-gaap	Premiums Written Net PremiumsWrittenNet	1157640000	usd
CY2023Q3	us-gaap	Premiums Written Net PremiumsWrittenNet	1058325000	usd
	us-gaap	Premiums Written Net PremiumsWrittenNet	3540362000	usd
	us-gaap	Premiums Written Net PremiumsWrittenNet	3143000000	usd
CY2024Q3	us-gaap	Direct Premiums Earned DirectPremiumsEarned	1279783000	usd
CY2023Q3	us-gaap	Direct Premiums Earned DirectPremiumsEarned	1123444000	usd
	us-gaap	Direct Premiums Earned DirectPremiumsEarned	3727847000	usd
	us-gaap	Direct Premiums Earned DirectPremiumsEarned	3229170000	usd
CY2024Q3	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	6972000	usd
CY2023Q3	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	8916000	usd
	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	18942000	usd
	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	21174000	usd
CY2024Q3	us-gaap	Ceded Premiums Earned CededPremiumsEarned	174527000	usd
CY2023Q3	us-gaap	Ceded Premiums Earned CededPremiumsEarned	150443000	usd
	us-gaap	Ceded Premiums Earned CededPremiumsEarned	503386000	usd
	us-gaap	Ceded Premiums Earned CededPremiumsEarned	423941000	usd
CY2024Q3	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	1112228000	usd
CY2023Q3	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	981917000	usd
	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	3243403000	usd
	us-gaap	Premiums Earned Net Property And Casualty PremiumsEarnedNetPropertyAndCasualty	2826403000	usd
CY2024Q3	us-gaap	Policyholder Benefits And Claims Incurred Gross PolicyholderBenefitsAndClaimsIncurredGross	1194224000	usd
CY2023Q3	us-gaap	Policyholder Benefits And Claims Incurred Gross PolicyholderBenefitsAndClaimsIncurredGross	741288000	usd
	us-gaap	Policyholder Benefits And Claims Incurred Gross PolicyholderBenefitsAndClaimsIncurredGross	2957610000	usd
	us-gaap	Policyholder Benefits And Claims Incurred Gross PolicyholderBenefitsAndClaimsIncurredGross	2053511000	usd
CY2024Q3	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Assumed ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed	6104000	usd
CY2023Q3	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Assumed ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed	8182000	usd
	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Assumed ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed	17143000	usd
	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Assumed ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed	19115000	usd
CY2024Q3	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	434670000	usd
CY2023Q3	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	103573000	usd
	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	579255000	usd
	us-gaap	Reinsurance Effect On Claims And Benefits Incurred Amount Ceded ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded	213161000	usd
CY2024Q3	us-gaap	Policyholder Benefits And Claims Incurred Net PolicyholderBenefitsAndClaimsIncurredNet	765658000	usd
CY2023Q3	us-gaap	Policyholder Benefits And Claims Incurred Net PolicyholderBenefitsAndClaimsIncurredNet	645897000	usd
	us-gaap	Policyholder Benefits And Claims Incurred Net PolicyholderBenefitsAndClaimsIncurredNet	2395498000	usd
	us-gaap	Policyholder Benefits And Claims Incurred Net PolicyholderBenefitsAndClaimsIncurredNet	1859465000	usd
CY2024Q3	sigi	Percentage Of Unpaid Nfip Claims Ceded By Federal Government PercentageOfUnpaidNFIPClaimsCededByFederalGovernment	1
	us-gaap	Schedule Of Liability For Unpaid Claims And Claims Adjustment Expense ScheduleOfLiabilityForUnpaidClaimsAndClaimsAdjustmentExpense	<div><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The table below provides a roll forward of the reserve for loss and loss expense for beginning and ending reserve balances:</span></div><div><span><br/></span></div><div><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><td style="width:70.537%"></td><td style="width:0.1%"></td><td style="width:0.1%"></td><td style="width:0.384%"></td><td style="width:0.1%"></td><td style="width:1.0%"></td><td style="width:12.496%"></td><td style="width:0.1%"></td><td style="width:0.1%"></td><td style="width:0.384%"></td><td style="width:0.1%"></td><td style="width:1.0%"></td><td style="width:12.499%"></td><td style="width:0.1%"></td></tr><tr><td colspan="3" style="border-top:1pt solid #000000;padding:0 1pt"></td><td colspan="3" style="border-top:1pt solid #000000;padding:0 1pt"></td><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<br/>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><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%">2024</span></td><td colspan="3" style="border-top:1pt solid #000000;padding:0 1pt"></td><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%">2023</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 period</span></td><td colspan="3" style="background-color:#ccffcc;border-top:1pt solid #000000;padding:0 1pt"></td><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%">5,336,911</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><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"></td><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%">5,144,821 </span></td><td style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></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%">Less: reinsurance recoverable on unpaid loss and loss expense, at beginning of period</span></td><td colspan="3" style="padding:0 1pt"></td><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%">618,601</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><td colspan="3" style="padding:0 1pt"></td><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%">757,513 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></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 period</span></td><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"></td><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%">4,718,310</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><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"></td><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%">4,387,308 </span></td><td style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></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%">Incurred loss and loss expense for claims occurring in the:</span></td><td colspan="3" style="padding:0 1pt"></td><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><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><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%">2,212,750</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><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"></td><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%">1,865,247 </span></td><td style="background-color:#ccffcc;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></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><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%">182,748</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><td colspan="3" style="padding:0 1pt"></td><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%">(5,782)</span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></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><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%">2,395,498</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><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"></td><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%">1,859,465 </span></td><td style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></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%">Paid loss and loss expense for claims occurring in the:</span></td><td colspan="3" style="padding:0 1pt"></td><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><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><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%">638,494</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><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"></td><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%">607,595 </span></td><td style="background-color:#ccffcc;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></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><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%">1,053,299</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><td colspan="3" style="padding:0 1pt"></td><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%">988,859 </span></td><td style="padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></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><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%">1,691,793</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><td colspan="3" style="background-color:#ccffcc;padding:0 1pt"></td><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%">1,596,454 </span></td><td style="background-color:#ccffcc;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></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%">Net reserve for loss and loss expense, at end of period</span></td><td colspan="3" style="padding:0 1pt"></td><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%">5,422,015</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><td colspan="3" style="padding:0 1pt"></td><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%">4,650,319 </span></td><td style="border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></td></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><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%">1,029,981</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><td colspan="3" style="background-color:#d0ffd0;padding:0 1pt"></td><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%">651,051 </span></td><td style="background-color:#d0ffd0;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"></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%">Gross reserve for loss and loss expense, at end of period</span></td><td colspan="3" style="padding:0 1pt"></td><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%">6,451,996</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><td colspan="3" style="padding:0 1pt"></td><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%">5,301,370 </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></tr></table></div>
CY2023Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	5336911000	usd
CY2022Q4	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	5144821000	usd
CY2022Q4	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	757513000	usd
CY2023Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	4718310000	usd
CY2022Q4	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	4387308000	usd
	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	2212750000	usd
	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Current Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense	1865247000	usd
	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	182748000	usd
	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	-5782000	usd
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	2395498000	usd
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1	1859465000	usd
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	638494000	usd
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Current Year1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1	607595000	usd
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	1053299000	usd
	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Claims Paid Prior Years1 LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1	988859000	usd
	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	1691793000	usd
	us-gaap	Payments For Losses And Loss Adjustment Expense PaymentsForLossesAndLossAdjustmentExpense	1596454000	usd
CY2024Q3	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	5422015000	usd
CY2023Q3	us-gaap	Liability For Unpaid Claims And Claims Adjustment Expense Net LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet	4650319000	usd
CY2024Q3	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	1029981000	usd
CY2023Q3	us-gaap	Reinsurance Recoverable For Unpaid Claims And Claims Adjustments ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments	651051000	usd
CY2024Q3	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	6451996000	usd
CY2023Q3	us-gaap	Liability For Claims And Claims Adjustment Expense LiabilityForClaimsAndClaimsAdjustmentExpense	5301370000	usd
	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	182700000	usd
	us-gaap	Supplemental Information For Property Casualty Insurance Underwriters Prior Year Claims And Claims Adjustment Expense SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense	-5800000	usd
	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	4	segment
CY2024Q3	us-gaap	Net Investment Income NetInvestmentIncome	117759000	usd
CY2023Q3	us-gaap	Net Investment Income NetInvestmentIncome	100863000	usd
	us-gaap	Net Investment Income NetInvestmentIncome	334250000	usd
	us-gaap	Net Investment Income NetInvestmentIncome	290065000	usd
CY2024Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	5389000	usd
CY2023Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	-6880000	usd
	us-gaap	Gain Loss On Investments GainLossOnInvestments	5051000	usd
	us-gaap	Gain Loss On Investments GainLossOnInvestments	-8962000	usd
CY2024Q3	sigi	Total Investments Revenue TotalInvestmentsRevenue	123148000	usd
CY2023Q3	sigi	Total Investments Revenue TotalInvestmentsRevenue	93983000	usd
	sigi	Total Investments Revenue TotalInvestmentsRevenue	339301000	usd
	sigi	Total Investments Revenue TotalInvestmentsRevenue	281103000	usd
CY2024Q3	us-gaap	Revenues Revenues	1244306000	usd
CY2023Q3	us-gaap	Revenues Revenues	1081081000	usd
	us-gaap	Revenues Revenues	3605270000	usd
	us-gaap	Revenues Revenues	3121425000	usd
CY2024Q3	us-gaap	Net Investment Income NetInvestmentIncome	117759000	usd
CY2023Q3	us-gaap	Net Investment Income NetInvestmentIncome	100863000	usd
	us-gaap	Net Investment Income NetInvestmentIncome	334250000	usd
	us-gaap	Net Investment Income NetInvestmentIncome	290065000	usd
CY2024Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	5389000	usd
CY2023Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	-6880000	usd
	us-gaap	Gain Loss On Investments GainLossOnInvestments	5051000	usd
	us-gaap	Gain Loss On Investments GainLossOnInvestments	-8962000	usd
CY2024Q3	sigi	Total Investments Revenue TotalInvestmentsRevenue	123148000	usd
CY2023Q3	sigi	Total Investments Revenue TotalInvestmentsRevenue	93983000	usd
	sigi	Total Investments Revenue TotalInvestmentsRevenue	339301000	usd
	sigi	Total Investments Revenue TotalInvestmentsRevenue	281103000	usd
CY2024Q3	sigi	Tax On Investment Income TaxOnInvestmentIncome	25511000	usd
CY2023Q3	sigi	Tax On Investment Income TaxOnInvestmentIncome	19191000	usd
	sigi	Tax On Investment Income TaxOnInvestmentIncome	70029000	usd
	sigi	Tax On Investment Income TaxOnInvestmentIncome	57092000	usd
CY2024Q3	sigi	Total Investment Segment Income After Federal Income Tax TotalInvestmentSegmentIncomeAfterFederalIncomeTax	97637000	usd
CY2023Q3	sigi	Total Investment Segment Income After Federal Income Tax TotalInvestmentSegmentIncomeAfterFederalIncomeTax	74792000	usd
	sigi	Total Investment Segment Income After Federal Income Tax TotalInvestmentSegmentIncomeAfterFederalIncomeTax	269272000	usd
	sigi	Total Investment Segment Income After Federal Income Tax TotalInvestmentSegmentIncomeAfterFederalIncomeTax	224011000	usd
CY2024Q3	us-gaap	Interest Expense Debt InterestExpenseDebt	7250000	usd
CY2023Q3	us-gaap	Interest Expense Debt InterestExpenseDebt	7186000	usd
	us-gaap	Interest Expense Debt InterestExpenseDebt	21633000	usd
	us-gaap	Interest Expense Debt InterestExpenseDebt	21610000	usd
CY2024Q3	us-gaap	Other General Expense OtherGeneralExpense	4662000	usd
CY2023Q3	us-gaap	Other General Expense OtherGeneralExpense	5871000	usd
	us-gaap	Other General Expense OtherGeneralExpense	29314000	usd
	us-gaap	Other General Expense OtherGeneralExpense	27308000	usd
CY2024Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	116487000	usd
CY2023Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	112517000	usd
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	138955000	usd
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	301433000	usd
CY2024Q3	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	2300000	usd
CY2023Q3	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	2300000	usd
	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	6900000	usd
	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	6900000	usd
CY2024Q3	sigi	Income Available To Common Stockholders Before Federal Income Tax IncomeAvailableToCommonStockholdersBeforeFederalIncomeTax	114187000	usd
CY2023Q3	sigi	Income Available To Common Stockholders Before Federal Income Tax IncomeAvailableToCommonStockholdersBeforeFederalIncomeTax	110217000	usd
	sigi	Income Available To Common Stockholders Before Federal Income Tax IncomeAvailableToCommonStockholdersBeforeFederalIncomeTax	132055000	usd
	sigi	Income Available To Common Stockholders Before Federal Income Tax IncomeAvailableToCommonStockholdersBeforeFederalIncomeTax	294533000	usd
CY2024Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	116487000	usd
CY2024Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	24209000	usd
CY2024Q3	us-gaap	Net Income Loss NetIncomeLoss	92278000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	187465000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	39367000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	148098000	usd
CY2024Q3	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Gross UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsGross	43927000	usd
CY2024Q3	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Tax UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsTax	9225000	usd
CY2024Q3	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Net UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsNet	34702000	usd
CY2024Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securitiesbefore Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesbeforeTax	-1249000	usd
CY2024Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesTax	-263000	usd
CY2024Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	-986000	usd
CY2024Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Gross DebtSecuritiesAvailableforsaleAllowanceforCreditLossGross	-2191000	usd
CY2024Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Tax DebtSecuritiesAvailableforsaleAllowanceforCreditLossTax	-459000	usd
CY2024Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	-1732000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	227952000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesTax	47870000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	180082000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-967000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-203000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-764000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-967000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-203000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-764000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	228919000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	48073000	usd
CY2024Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	180846000	usd
CY2024Q3	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	345406000	usd
CY2024Q3	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	72282000	usd
CY2024Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	273124000	usd
CY2023Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	112517000	usd
CY2023Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	23309000	usd
CY2023Q3	us-gaap	Net Income Loss NetIncomeLoss	89208000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-101722000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-21361000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-80361000	usd
CY2023Q3	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Gross UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsGross	-32898000	usd
CY2023Q3	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Tax UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsTax	-6909000	usd
CY2023Q3	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Net UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsNet	-25989000	usd
CY2023Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securitiesbefore Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesbeforeTax	4628000	usd
CY2023Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesTax	972000	usd
CY2023Q3	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	3656000	usd
CY2023Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Gross DebtSecuritiesAvailableforsaleAllowanceforCreditLossGross	2468000	usd
CY2023Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Tax DebtSecuritiesAvailableforsaleAllowanceforCreditLossTax	519000	usd
CY2023Q3	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	1949000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	-127524000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesTax	-26779000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-100745000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-756000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-158000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	-598000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-756000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-158000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-598000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-126768000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-26621000	usd
CY2023Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-100147000	usd
CY2023Q3	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	-14251000	usd
CY2023Q3	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	-3312000	usd
CY2023Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-10939000	usd
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	138955000	usd
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	27478000	usd
	us-gaap	Net Income Loss NetIncomeLoss	111477000	usd
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	163558000	usd
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	34347000	usd
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	129211000	usd
	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Gross UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsGross	37090000	usd
	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Tax UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsTax	7789000	usd
	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Net UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsNet	29301000	usd
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securitiesbefore Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesbeforeTax	-1284000	usd
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesTax	-270000	usd
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	-1014000	usd
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Gross DebtSecuritiesAvailableforsaleAllowanceforCreditLossGross	1692000	usd
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Tax DebtSecuritiesAvailableforsaleAllowanceforCreditLossTax	356000	usd
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	1336000	usd
	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	201056000	usd
	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesTax	42222000	usd
	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	158834000	usd
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-2901000	usd
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-609000	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	-2292000	usd
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-2901000	usd
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-609000	usd
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-2292000	usd
	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	203957000	usd
	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	42831000	usd
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	161126000	usd
	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	342912000	usd
	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	70309000	usd
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	272603000	usd
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	301433000	usd
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	61043000	usd
	us-gaap	Net Income Loss NetIncomeLoss	240390000	usd
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-96478000	usd
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-20259000	usd
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-76219000	usd
	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Gross UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsGross	-16497000	usd
	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Tax UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsTax	-3465000	usd
	sigi	Unrealized Gains Losses On Securities With Credit Loss Recognized In Earnings Net UnrealizedGainsLossesOnSecuritiesWithCreditLossRecognizedInEarningsNet	-13032000	usd
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securitiesbefore Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesbeforeTax	20115000	usd
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesTax	4224000	usd
	sigi	Oci Reclassification Adjustmentfrom Aoc Ifor Writedownof Securities Netof Tax OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax	15891000	usd
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Gross DebtSecuritiesAvailableforsaleAllowanceforCreditLossGross	-7925000	usd
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Tax DebtSecuritiesAvailableforsaleAllowanceforCreditLossTax	-1664000	usd
	sigi	Debt Securities Availableforsale Allowancefor Credit Loss Net DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet	-6261000	usd
	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	-100785000	usd
	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesTax	-21164000	usd
	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-79621000	usd
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax	-2270000	usd
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax	-476000	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	-1794000	usd
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-2270000	usd
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-476000	usd
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-1794000	usd
	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-98515000	usd
	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-20688000	usd
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-77827000	usd
	sigi	Comprehensive Income Loss Before Tax ComprehensiveIncomeLossBeforeTax	202918000	usd
	sigi	Comprehensive Income Loss Tax ComprehensiveIncomeLossTax	40355000	usd
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	162563000	usd
CY2020Q4	srt	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	100000000	usd
	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	103000	shares
	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	8700000	usd
CY2024Q3	us-gaap	Stock Repurchase Program Remaining Authorized Repurchase Amount1 StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1	75500000	usd
CY2024Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	89978000	usd
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	233490000	usd
CY2024Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	60877000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	60609000	shares
	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	339000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	60948000	shares
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.85
CY2024Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.47
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.71
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.83
CY2024Q3	sigi	Number Of Insurance Subsidiaries NumberOfInsuranceSubsidiaries	10	subsidiary
CY2024Q3	ecd	Non Rule10b51 Arr Adopted Flag NonRule10b51ArrAdoptedFlag	false
CY2024Q3	ecd	Rule10b51 Arr Adopted Flag Rule10b51ArrAdoptedFlag	false
CY2024Q3	ecd	Non Rule10b51 Arr Trmntd Flag NonRule10b51ArrTrmntdFlag	false
CY2024Q3	ecd	Rule10b51 Arr Trmntd Flag Rule10b51ArrTrmntdFlag	false

Files In Submission

Name	View Source	Status
0000230557-24-000026-index-headers.html	Edgar Link	pending
0000230557-24-000026-index.html	Edgar Link	pending
0000230557-24-000026.txt	Edgar Link	pending
0000230557-24-000026-xbrl.zip	Edgar Link	pending
Financial_Report.xlsx	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
R1.htm	Edgar Link	pending
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FilingSummary.xml	Edgar Link	unprocessable
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report.css	Edgar Link	pending
Show.js	Edgar Link	pending
sigi-20240930.htm	Edgar Link	pending
sigi-20240930.xsd	Edgar Link	pending
sigi-20240930_g1.jpg	Edgar Link	pending
sigi-ex311_9302024xq3.htm	Edgar Link	pending
sigi-ex312_9302024xq3.htm	Edgar Link	pending
sigi-ex321_9302024xq3.htm	Edgar Link	pending
sigi-ex322_9302024xq3.htm	Edgar Link	pending
sigi-20240930_cal.xml	Edgar Link	unprocessable
sigi-20240930_def.xml	Edgar Link	unprocessable
sigi-20240930_lab.xml	Edgar Link	unprocessable
sigi-20240930_pre.xml	Edgar Link	unprocessable
sigi-20240930_htm.xml	Edgar Link	completed

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$SIGI
Selective Insurance Group Inc Stock $sigi

2024 Q4 Form 10-Q Financial Statement

#000023055724000026 Filed on October 25, 2024

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$SIGI Selective Insurance Group Inc Stock $sigi

2024 Q4 Form 10-Q Financial Statement

#000023055724000026 Filed on October 25, 2024

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$SIGI
Selective Insurance Group Inc Stock $sigi