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Long-Term Debt (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Jul. 06, 2021
Debt Instrument [Line Items] |  |  |  |
Long-term debt | $ 508 | $ 639 |  |
Debt Instrument, Interest Rate, Effective Percentage | 6.60% |  |  |
Net realized gains on extinguishment of debt | $ 0 | 81 | $ 33 |
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months | 519 |  |  |
Long-term Debt, Maturities, Repayments of Principal in Year Two | 0 |  |  |
Long-term Debt, Maturities, Repayments of Principal in Year Three | 0 |  |  |
Long-term Debt, Maturities, Repayments of Principal in Year Four | 0 |  |  |
Long-term Debt, Maturities, Repayments of Principal in Year Five | 0 |  |  |
Paydown of Ambac Note |  |  | 1,641 |
Long-term Debt, Maturities, Repayments of Principal after Year Five | 41 |  |  |
5.1% Junior Surplus Notes, General Account Due 2020 Plus Accrued Interest | $ 475 |  |  |
Tier 2 Notes [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 8.50% |  |  |
Debt Instrument, Interest Rate, Effective Percentage | 9.90% |  |  |
Debt Instrument, Face Amount | $ 0 |  |  |
Paid-in-Kind Interest | 0 | 49 |  |
5.1% Junior Surplus Notes, General Account Due 2020 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt Instrument, Issued, Principal |  |  | 280 |
Ambac Assurance Corporation [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt | 508 | 639 |  |
Long-term Debt, Gross | 560 | 706 |  |
Debt Instrument, Unamortized Discount (Premium), Net | (52) | (67) |  |
Ambac Assurance Corporation [Member] | 5.1% Surplus Notes, General Account, Due 2020 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt | 491 | 477 |  |
Long-term Debt, Gross | 519 | 519 |  |
Debt Instrument, Unamortized Discount (Premium), Net | (28) | (42) |  |
Ambac Assurance Corporation [Member] | Tier 2 Notes [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Long-term debt | 0 | 146 |  |
Long-term Debt, Gross | 0 | 146 |  |
Debt Instrument, Unamortized Discount (Premium), Net | 0 | 0 |  |
Ambac Assurance Corporation [Member] | Sitka AAC Note |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Net realized gains on extinguishment of debt | $ 53 |  |  |
Ambac UK [Member] | Secured Debt [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 0.00% |  |  |
Long-term debt | $ 17 | 16 |  |
Long-term Debt, Gross | 41 | 41 |  |
Debt Instrument, Unamortized Discount (Premium), Net | $ (24) | (25) |  |
Debt Instrument, Interest Rate, Effective Percentage | 7.40% |  |  |
Sitka Holdings, LLC | LIBOR + 4.5% Senor Secured Notes Due 2026 |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt Instrument, Face Amount |  |  |  | $ 1,175
5.1% Surplus Notes, General Account, Due 2020 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Net realized gains on extinguishment of debt |  | 134 |  |
Debt Instrument, Repurchased During Period | $ 266 |  |  |
5.1% Junior Surplus Notes, General Account Due 2020 [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Net realized gains on extinguishment of debt |  |  | $ 33 |
Consolidated Variable Interest Entities [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Unpaid Principal Amount Of Fixed Rate Debt Accounted For Under Fair Value Option | 3,655 | $ 3,388 |  |
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months | 0 |  |  |
Long-term Debt, Maturities, Repayments of Principal in Year Two | 0 |  |  |
Long-term Debt, Maturities, Repayments of Principal in Year Three | 0 |  |  |
Long-term Debt, Maturities, Repayments of Principal in Year Four | 0 |  |  |
Long-term Debt, Maturities, Repayments of Principal in Year Five | 0 |  |  |
Long-term Debt, Maturities, Repayments of Principal after Year Five | $ 3,655 |  |  |
Consolidated Variable Interest Entities [Member] | Minimum [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt Instrument, Interest Rate, Effective Percentage | 0.00% | 0.00% |  |
Consolidated Variable Interest Entities [Member] | Maximum [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt Instrument, Interest Rate, Effective Percentage | 22.20% | 7.93% |  |
London Interbank Offered Rate (LIBOR) [Member] | LIBOR + 4.5% Senor Secured Notes Due 2026 |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  | 4.50%

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