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Fair Value Measurements - Summary of Carrying Amount and Fair Value of Ambac's Financial Assets and Liabilities (Details) - USD ($) $ in Thousands | Mar. 31, 2024 | Dec. 31, 2023 | Mar. 31, 2023
--- | --- | --- | ---
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | $ 2,095,000 |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 2,000 | $ 3,000 | $ 1,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 37,000 | 40,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 75,000 | 71,000 |
Financial assets: |  |  |
Derivative assets | 21,000 | 26,000 |
Other assets | 0 |  |
Long-term Debt | 512,000 | 508,000 |
Financial liabilities: |  |  |
Derivative liabilities | 29,000 | 35,000 |
Equity Securities Excluded From Fair Value Table | 13,000 | 13,000 |
Debt Securities, Available-for-sale, Amortized Cost | 2,135,000 | 2,197,000 |
Debt Securities, Available-for-Sale, Current | 2,095,000 | 2,162,000 |
Fixed Income Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 1,687,000 | 1,710,000 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 2,000 | 3,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 37,000 | 40,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 74,000 | 71,000 |
Financial liabilities: |  |  |
Debt Securities, Available-for-sale, Amortized Cost | 1,726,000 | 1,744,000 |
Fixed Income Investments And Other Investments [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 2,068,000 | 2,135,000 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 2,000 | 3,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 37,000 | 40,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 74,000 | 71,000 |
Financial liabilities: |  |  |
Debt Securities, Available-for-sale, Amortized Cost | 2,108,000 | 2,170,000 |
Commercial Mortgage Backed Securities [Member] | Fixed Income Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 27,000 |  |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0 |
Financial liabilities: |  |  |
Debt Securities, Available-for-sale, Amortized Cost | 27,000 |  |
Short-term Investments [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 382,000 | 426,000 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0 |
Financial liabilities: |  |  |
Debt Securities, Available-for-sale, Amortized Cost | 382,000 | 426,000 |
Asset-backed Securities [Member] | Fixed Income Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 231,000 | 303,000 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 3,000 | 3,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 5,000 | 1,000 |
Financial liabilities: |  |  |
Debt Securities, Available-for-sale, Amortized Cost | 232,000 | 301,000 |
Collateralized Debt Obligations [Member] | Fixed Income Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 143,000 | 139,000 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 1,000 | 1,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 1,000 |
Financial liabilities: |  |  |
Debt Securities, Available-for-sale, Amortized Cost | 143,000 | 139,000 |
Residential Mortgage-Backed Securities [Member] | Fixed Income Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 253,000 | 250,000 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 2,000 | 3,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 28,000 | 28,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 12,000 | 14,000 |
Financial liabilities: |  |  |
Debt Securities, Available-for-sale, Amortized Cost | 239,000 | 239,000 |
US Government Debt Securities [Member] | Fixed Income Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 98,000 | 82,000 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 1,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 4,000 | 4,000 |
Financial liabilities: |  |  |
Debt Securities, Available-for-sale, Amortized Cost | 101,000 | 85,000 |
Debt Security, Government, Non-US [Member] | Fixed Income Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 99,000 | 100,000 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 1,000 | 1,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 7,000 | 6,000 |
Financial liabilities: |  |  |
Debt Securities, Available-for-sale, Amortized Cost | 105,000 | 105,000 |
Corporate Debt Securities [Member] | Fixed Income Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 765,000 | 745,000 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 3,000 | 4,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 45,000 | 44,000 |
Financial liabilities: |  |  |
Debt Securities, Available-for-sale, Amortized Cost | 807,000 | 785,000 |
Municipal Bonds [Member] | Fixed Income Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 72,000 | 72,000 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 1,000 | 1,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 1,000 | 1,000 |
Financial liabilities: |  |  |
Debt Securities, Available-for-sale, Amortized Cost | 72,000 | 72,000 |
Collateralized Mortgage Backed Securities [Member] | Fixed Income Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 27,000 | 19,000 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0 |
Financial liabilities: |  |  |
Debt Securities, Available-for-sale, Amortized Cost | 27,000 | 19,000 |
Total Fair Value [Member] |  |  |
Financial assets: |  |  |
Cash | 44,000 | 28,000 |
Reported Value Measurement [Member] |  |  |
Financial assets: |  |  |
Other investments | 152,000 | 77,000 |
Cash | 44,000 | 28,000 |
Loans | 2,000 | 2,000 |
Total financial assets | 6,987,000 | 7,022,000 |
Financial liabilities: |  |  |
Liabilities for net financial guarantees written | 231,000 | 292,000 |
Long-term debt | 999,000 | 983,000 |
Total financial liabilities | 5,354,000 | 5,474,000 |
Reported Value Measurement [Member] | Short-term Investments [Member] |  |  |
Financial assets: |  |  |
Short term investments | 382,000 | 426,000 |
Reported Value Measurement [Member] | Other Debt Obligations [Member] |  |  |
Financial assets: |  |  |
Other investments | 558,000 | 475,000 |
Reported Value Measurement [Member] | Interest Rate Swap [Member] |  |  |
Financial liabilities: |  |  |
Derivative liabilities | 29,000 | 35,000 |
Reported Value Measurement [Member] | Interest Rate Swap [Member] | Other Assets [Member] |  |  |
Financial assets: |  |  |
Derivative assets | 21,000 | 25,000 |
Reported Value Measurement [Member] | Warrants [Member] |  |  |
Financial assets: |  |  |
Derivative assets | 1,000 | 1,000 |
Level 1 [Member] |  |  |
Financial assets: |  |  |
Cash | 44,000 | 27,000 |
Total financial assets | 1,049,000 | 979,000 |
Financial liabilities: |  |  |
Liabilities for net financial guarantees written | 0 | 0 |
Long-term debt | 0 | 0 |
Total financial liabilities | 0 | 0 |
Level 1 [Member] | Short-term Investments [Member] |  |  |
Financial assets: |  |  |
Short term investments | 379,000 | 421,000 |
Level 1 [Member] | Loans Receivable [Member] |  |  |
Financial assets: |  |  |
Loans | 0 | 0 |
Level 1 [Member] | Other Debt Obligations [Member] |  |  |
Financial assets: |  |  |
Other investments | 152,000 | 77,000 |
Level 1 [Member] | Interest Rate Swap [Member] |  |  |
Financial liabilities: |  |  |
Derivative liabilities | 0 | 0 |
Level 1 [Member] | Interest Rate Swap [Member] | Other Assets [Member] |  |  |
Financial assets: |  |  |
Derivative assets | 0 | 0 |
Level 1 [Member] | Warrants [Member] |  |  |
Financial assets: |  |  |
Derivative assets | 0 | 0 |
Level 2 [Member] |  |  |
Financial assets: |  |  |
Cash | 0 | 2,000 |
Total financial assets | 1,747,000 | 1,795,000 |
Financial liabilities: |  |  |
Liabilities for net financial guarantees written | 0 | 0 |
Long-term debt | 753,000 | 679,000 |
Total financial liabilities | 4,670,000 | 4,671,000 |
Level 2 [Member] | Short-term Investments [Member] |  |  |
Financial assets: |  |  |
Short term investments | 2,000 | 5,000 |
Level 2 [Member] | Loans Receivable [Member] |  |  |
Financial assets: |  |  |
Loans | 0 | 0 |
Level 2 [Member] | Other Debt Obligations [Member] |  |  |
Financial assets: |  |  |
Other investments | 0 | 0 |
Level 2 [Member] | Interest Rate Swap [Member] |  |  |
Financial liabilities: |  |  |
Derivative liabilities | 29,000 | 35,000 |
Level 2 [Member] | Interest Rate Swap [Member] | Other Assets [Member] |  |  |
Financial assets: |  |  |
Derivative assets | 0 | 0 |
Level 2 [Member] | Warrants [Member] |  |  |
Financial assets: |  |  |
Derivative assets | 0 | 0 |
Level 3 [Member] |  |  |
Financial assets: |  |  |
Cash | 0 | 0 |
Total financial assets | 3,783,000 | 3,850,000 |
Financial liabilities: |  |  |
Liabilities for net financial guarantees written | 498,000 | 788,000 |
Long-term debt | 19,000 | 18,000 |
Total financial liabilities | 718,000 | 1,026,000 |
Level 3 [Member] | Short-term Investments [Member] |  |  |
Financial assets: |  |  |
Short term investments | 0 | 0 |
Level 3 [Member] | Loans Receivable [Member] |  |  |
Financial assets: |  |  |
Loans | 2,000 | 2,000 |
Level 3 [Member] | Other Debt Obligations [Member] |  |  |
Financial assets: |  |  |
Other investments | 0 | 0 |
Level 3 [Member] | Interest Rate Swap [Member] |  |  |
Financial liabilities: |  |  |
Derivative liabilities | 0 | 0 |
Level 3 [Member] | Interest Rate Swap [Member] | Other Assets [Member] |  |  |
Financial assets: |  |  |
Derivative assets | 21,000 | 25,000 |
Level 3 [Member] | Warrants [Member] |  |  |
Financial assets: |  |  |
Derivative assets | 1,000 | 1,000 |
Commercial Mortgage Backed Securities [Member] | Reported Value Measurement [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 27,000 | 19,000 |
Municipal Bonds [Member] | Reported Value Measurement [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 101,000 | 99,000 |
Corporate Debt Securities [Member] | Reported Value Measurement [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 765,000 | 745,000 |
Debt Security, Government, Non-US [Member] | Reported Value Measurement [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 99,000 | 100,000 |
US Government Debt Securities [Member] | Reported Value Measurement [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 98,000 | 82,000 |
Residential Mortgage-Backed Securities [Member] | Reported Value Measurement [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 253,000 | 250,000 |
Collateralized Debt Obligations [Member] | Reported Value Measurement [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 143,000 | 139,000 |
Asset-backed Securities [Member] | Reported Value Measurement [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 231,000 | 303,000 |
Fair Value, Recurring [Member] |  |  |
Financial assets: |  |  |
Total financial assets | 6,974,000 | 7,010,000 |
Financial liabilities: |  |  |
Liabilities for net financial guarantees written | 498,000 | 788,000 |
Long-term debt | 772,000 | 697,000 |
Total financial liabilities | 5,388,000 | 5,697,000 |
Fair Value, Recurring [Member] | Commercial Mortgage Backed Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 27,000 | 19,000 |
Fair Value, Recurring [Member] | Short-term Investments [Member] |  |  |
Financial assets: |  |  |
Short term investments | 382,000 | 426,000 |
Fair Value, Recurring [Member] | Loans Receivable [Member] |  |  |
Financial assets: |  |  |
Loans | 2,000 | 2,000 |
Fair Value, Recurring [Member] | Other Debt Obligations [Member] |  |  |
Financial assets: |  |  |
Other investments | 546,000 | 463,000 |
Fair Value, Recurring [Member] | Asset-backed Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 231,000 | 303,000 |
Fair Value, Recurring [Member] | Collateralized Debt Obligations [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 143,000 | 139,000 |
Fair Value, Recurring [Member] | Residential Mortgage-Backed Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 253,000 | 250,000 |
Fair Value, Recurring [Member] | US Government Debt Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 98,000 | 82,000 |
Fair Value, Recurring [Member] | Debt Security, Government, Non-US [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 99,000 | 100,000 |
Fair Value, Recurring [Member] | Corporate Debt Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 765,000 | 745,000 |
Fair Value, Recurring [Member] | Municipal Bonds [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 101,000 | 99,000 |
Fair Value, Recurring [Member] | Interest Rate Swap [Member] |  |  |
Financial liabilities: |  |  |
Derivative liabilities | 29,000 | 35,000 |
Fair Value, Recurring [Member] | Interest Rate Swap [Member] | Other Assets [Member] |  |  |
Financial assets: |  |  |
Derivative assets | 21,000 | 25,000 |
Fair Value, Recurring [Member] | Warrants [Member] |  |  |
Financial assets: |  |  |
Derivative assets | 1,000 | 1,000 |
Fair Value, Recurring [Member] | Level 1 [Member] | Commercial Mortgage Backed Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 0 |
Fair Value, Recurring [Member] | Level 1 [Member] | Asset-backed Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 0 |
Fair Value, Recurring [Member] | Level 1 [Member] | Collateralized Debt Obligations [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 0 |
Fair Value, Recurring [Member] | Level 1 [Member] | Residential Mortgage-Backed Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 0 |
Fair Value, Recurring [Member] | Level 1 [Member] | US Government Debt Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 98,000 | 82,000 |
Fair Value, Recurring [Member] | Level 1 [Member] | Debt Security, Government, Non-US [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 99,000 | 100,000 |
Fair Value, Recurring [Member] | Level 1 [Member] | Corporate Debt Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 0 |
Fair Value, Recurring [Member] | Level 1 [Member] | Municipal Bonds [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 0 |
Fair Value, Recurring [Member] | Level 2 [Member] | Commercial Mortgage Backed Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 27,000 | 19,000 |
Fair Value, Recurring [Member] | Level 2 [Member] | Asset-backed Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 163,000 | 235,000 |
Fair Value, Recurring [Member] | Level 2 [Member] | Collateralized Debt Obligations [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 143,000 | 139,000 |
Fair Value, Recurring [Member] | Level 2 [Member] | Residential Mortgage-Backed Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 253,000 | 250,000 |
Fair Value, Recurring [Member] | Level 2 [Member] | US Government Debt Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 0 |
Fair Value, Recurring [Member] | Level 2 [Member] | Debt Security, Government, Non-US [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 0 |
Fair Value, Recurring [Member] | Level 2 [Member] | Corporate Debt Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 746,000 | 726,000 |
Fair Value, Recurring [Member] | Level 2 [Member] | Municipal Bonds [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 101,000 | 99,000 |
Fair Value, Recurring [Member] | Level 3 [Member] | Commercial Mortgage Backed Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 0 |
Fair Value, Recurring [Member] | Level 3 [Member] | Asset-backed Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 68,000 | 68,000 |
Fair Value, Recurring [Member] | Level 3 [Member] | Collateralized Debt Obligations [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 0 |
Fair Value, Recurring [Member] | Level 3 [Member] | Residential Mortgage-Backed Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 0 |
Fair Value, Recurring [Member] | Level 3 [Member] | US Government Debt Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 0 |
Fair Value, Recurring [Member] | Level 3 [Member] | Debt Security, Government, Non-US [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 0 |
Fair Value, Recurring [Member] | Level 3 [Member] | Corporate Debt Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 19,000 | 19,000 |
Fair Value, Recurring [Member] | Level 3 [Member] | Municipal Bonds [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 0 |
Collateral Pledged [Member] | Fixed Income Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 26,000 | 27,000 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 1,000 | 0 |
Financial liabilities: |  |  |
Debt Securities, Available-for-sale, Amortized Cost | 27,000 | 0 |
Collateral Pledged [Member] | Short-term Investments [Member] | Fixed Income Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 27,000 |
Debt Securities, Available-for-sale, Allowance for Credit Loss | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0 |
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | 0 | 0 |
Financial liabilities: |  |  |
Debt Securities, Available-for-sale, Amortized Cost | 0 | 27,000 |
Collateral Pledged [Member] | US Government Debt Securities [Member] | Reported Value Measurement [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 26,000 | 0 |
Collateral Pledged [Member] | Short-term Investments [Member] | Reported Value Measurement [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 27,000 |
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Short-term Investments [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 0 | 27,000 |
Collateral Pledged [Member] | Fair Value, Recurring [Member] | US Government Debt Securities [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
Fixed maturity securities, at fair value | 26,000 | 0 |
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Level 1 [Member] | Short-term Investments [Member] |  |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |  |
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