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Investments - Additional Information (Details) - USD ($) $ in Thousands | Jun. 30, 2024 | Dec. 31, 2023 | Jun. 30, 2023
--- | --- | --- | ---
Schedule of Investments [Line Items] |  |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss | $ 3,000 | $ 3,000 | $ 1,000
Securities fair value | 29,000 | 24,000 |
Debt Securities, Available-for-sale, Unrealized Loss Position | 1,159,000 | 1,032,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 78,000 | 71,000 |
Debt Securities, Available for sale, Unrealized Loss Position, Accumulated Loss, Including Pledged Securities | $ 1,184,000 |  |
Average Percentage of Unrealized Loss Versus Amortized Cost for Below Investment Grade Securities | 8.00% |  |
Average Percentage of Unrealized Loss Versus Amortized Cost for Investment Grade Securities | 7.00% |  |
Fiduciary Funds Held by Insurance Distribution Subsidiaries | $ 2,000 | 2,000 |
Investment Portfolio [Member] |  |  |
Schedule of Investments [Line Items] |  |  |
Fair Value of Cash and Securities Pledged to Derivative Counterparties | 25,000 | 27,000 |
Fixed Income Securities [Member] |  |  |
Schedule of Investments [Line Items] |  |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 3,000 | 3,000 |
Debt Securities, Available-for-sale, Unrealized Loss Position | 1,113,000 | 1,028,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 77,000 | 71,000 |
Fixed Income Securities [Member] | Corporate Debt Securities [Member] |  |  |
Schedule of Investments [Line Items] |  |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Unrealized Loss Position | 618,000 | 584,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 46,000 | 44,000 |
Fixed Income Securities [Member] | Corporate Debt Securities [Member] | External Credit Rating, Investment Grade |  |  |
Schedule of Investments [Line Items] |  |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 45,000 |  |
Fixed Income Securities [Member] | Corporate Debt Securities [Member] | External Credit Rating, Non Investment Grade [Member] |  |  |
Schedule of Investments [Line Items] |  |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 483 |  |
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member] |  |  |
Schedule of Investments [Line Items] |  |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 3,000 | 3,000 |
Debt Securities, Available-for-sale, Unrealized Loss Position | 129,000 | 104,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 13,000 | 14,000 |
Fixed Income Securities [Member] | Asset-backed Securities [Member] |  |  |
Schedule of Investments [Line Items] |  |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Unrealized Loss Position | 117,000 | 92,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 5,000 | 1,000 |
Reported Value Measurement [Member] |  |  |
Schedule of Investments [Line Items] |  |  |
Other investments | 153,000 | 77,000 |
Reported Value Measurement [Member] | Interest Rate Contract [Member] |  |  |
Schedule of Investments [Line Items] |  |  |
Other investments | $ 89,000 | $ 39,000 |

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