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Investments - Narrative (Details) - USD ($) | 9 Months Ended |
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items] |  |  |
Mortgage- and Asset-backed Securities Not Due at a Single Maturity Date | $ 1,658,900,000 |  |
Financing Receivable, Accrued Interest, before Allowance for Credit Loss | 73,500,000 |  | $ 70,900,000
Equity securities, FV-NI, unrealized gain (loss) | $ (2,300,000) | $ (2,300,000) |
Percentage of Equity Method Limited Liability Investments reported with a lag | 3.00% |  |
Percentage of Equity Method Limited Liability Investments reported with a One Month Lag | 2.00% |  |
Loans to Policyholders | $ 279,300,000 |  | 280,700,000
Equity Securities at Modified Cost | 22,200,000 |  | 22,500,000
Equity securities without readily determinable fair value, impairment loss, cumulative amount | 3,200,000 |  | 3,200,000
Equity Securities |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Other Asset Impairment Charges | 0 | $ 400,000 |
Alternative Energy Partnership Investments |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Alternative Energy Partnership Investments | 17,400,000 |  | 17,600,000
Investments in Fixed Maturities |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Other Receivables | 4,200,000 |  | 1,800,000
Other liabilities | 7,800,000 |  | 11,600,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss | 728,000,000.0 |  | 889,500,000
Government National Mortgage Association Certificates and Obligations (GNMA) |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Mortgage- and Asset-backed Securities Not Due at a Single Maturity Date | 326,100,000 |  |
Federal National Mortgage Association Certificates and Obligations (FNMA) |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Mortgage- and Asset-backed Securities Not Due at a Single Maturity Date | 85,400,000 |  |
Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Mortgage- and Asset-backed Securities Not Due at a Single Maturity Date | 58,700,000 |  |
Other Non-Governmental Issuers |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Mortgage- and Asset-backed Securities Not Due at a Single Maturity Date | 1,188,700,000 |  |
Equity Securities |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Other Receivables |  |  | 300,000
Other liabilities | 0 |  | 0
Equity Method Investments |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Other liabilities | 0 |  | 0
Consolidated Entity, Excluding VIE |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Other Receivables | 185,000,000.0 |  | 185,700,000
Equity Securities, FV-NI, Current | 302,000,000.0 |  | 218,500,000
Alternative Energy Partnership Investments | 174,900,000 |  | 186,300,000
Loans to Policyholders | 279,300,000 |  | 280,700,000
Variable Interest Entity, Not Primary Beneficiary | Equity Method Limited Liability Investments |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Outstanding commitments to fund equity method limited liability investments | 102,600,000 |  |
Investment grade | Investments in Fixed Maturities |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt securities, available-for-sale, unrealized loss position, accumulated loss | 708,000,000.0 |  | 875,300,000
Non-investment-grade | Investments in Fixed Maturities |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Debt securities, available-for-sale, unrealized loss position, accumulated loss | $ 20,000,000.0 |  | $ 14,200,000
Percentage of unrealized loss position to amortized cost basis of available for sale security average | 4.40% |  | 4.90%

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