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Long-Term Debt (Details) - USD ($) $ in Millions | 12 Months Ended | 36 Months Ended |
--- | --- | --- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Jul. 06, 2026 | Feb. 12, 2018
Debt Instrument [Line Items] |  |  |  |  |
Tier 2 Note Security in RMBS Litigation Settlement Proceeds |  |  |  |  | $ 1,600
Long-term debt | $ 2,230 | $ 2,739 |  |  |
Debt Instrument, Interest Rate, Effective Percentage | 8.90% |  |  |  |
Net realized gains (losses) on extinguishment of debt | $ 33 | 0 | $ 0 |  |
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months | 785 |  |  |  |
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 | 1,175 |  |  |  |
Paydown of Ambac Note | 1,641 | 121 | 178 |  |
Long-term Debt, Maturities, Repayments of Principal after Year Five | 373 |  |  |  |
Make Whole Percentage of Principal |  |  |  | 103.00% |
Reb & Warranty Subrogation Recoveries Up To | 1,400 |  |  |  |
Aggregate Par Amount Reissued | $ 255 |  |  |  |
Discretionary Tier 2 Note Mandatory and Optional Redemption Percent by AAC | 100.00% |  |  |  |
Ambac Note Post Exit From Rehabilitation [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Paydown of Ambac Note | $ (1,641) | (121) | $ (178) |  |
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 | $ 333 |  |  |  |
Paid-in-Kind Interest | $ 93 | 66 |  |  |
5.1% Surplus Notes, General Account, Due 2020 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt Instrument, Interest Rate, Effective Percentage | 10.10% |  |  |  |
Sitka AAC Note |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt Instrument, Interest Rate, Effective Percentage | 5.70% |  |  |  |
Debt Instrument, Redemption Price, Percentage |  |  |  | 100.00% |
Ambac Assurance Corporation [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | $ 2,230 | 2,739 |  |  |
Long-term Debt, Gross | 2,334 | 2,884 |  |  |
Debt Instrument, Unamortized Discount (Premium), Net | (104) | (145) |  |  |
Ambac Assurance Corporation [Member] | 5.1% Junior Surplus Notes, General Account Due 2020 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | 0 | 247 |  |  |
Long-term Debt, Gross | 0 | 365 |  |  |
Debt Instrument, Unamortized Discount (Premium), Net | 0 | (118) |  |  |
Ambac Assurance Corporation [Member] | Ambac Note Post Exit From Rehabilitation [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | 0 | 1,641 |  |  |
Long-term Debt, Gross | 0 | 1,641 |  |  |
Debt Instrument, Unamortized Discount (Premium), Net | 0 | 0 |  |  |
Ambac Assurance Corporation [Member] | Tier 2 Notes [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | 333 | 306 |  |  |
Long-term Debt, Gross | 333 | 306 |  |  |
Debt Instrument, Unamortized Discount (Premium), Net | 0 | 0 |  |  |
Ambac Assurance Corporation [Member] | 5.1% Surplus Notes, General Account, Due 2020 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | 729 | 531 |  |  |
Long-term Debt, Gross | 785 | 531 |  |  |
Debt Instrument, Unamortized Discount (Premium), Net | (56) | 0 |  |  |
Ambac Assurance Corporation [Member] | Sitka AAC Note |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term debt | 1,154 | 0 |  |  |
Debt Instrument, Unamortized Discount (Premium), Net | (21) | 0 |  |  |
Debt Instrument, Face Amount | $ 1,175 | 0 |  |  |
Ambac UK [Member] | Secured Debt [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 0.00% |  |  |  |
Long-term debt | $ 15 | 14 |  |  |
Long-term Debt, Gross | 41 | 41 |  |  |
Debt Instrument, Unamortized Discount (Premium), Net | $ (26) | $ (27) |  |  |
Debt Instrument, Interest Rate, Effective Percentage | 7.40% |  |  |  |
5.1% Junior Surplus Notes Due 2020 [Member] | Ambac Assurance Corporation [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 5.10% | 5.10% |  |  |
5.1 % Surplus Notes Due 2020 [Member] | Ambac Assurance Corporation [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 5.10% | 5.10% |  |  |
Consolidated Variable Interest Entities [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Unpaid Principal Amount Of Fixed Rate Debt Accounted For Under Fair Value Option | $ 3,739 | $ 3,927 |  |  |
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 | 56 |  |  |  |
Long-term Debt, Maturities, Repayments of Principal in Year Five | 0 |  |  |  |
Long-term Debt, Maturities, Repayments of Principal after Year Five | $ 3,683 |  |  |  |
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 | 7.93% | 7.93% |  |  |
London Interbank Offered Rate (LIBOR) [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Interest Rate on Ambac Note Post Exit From Rehabilitation | 5.00% |  |  |  |
London Interbank Offered Rate (LIBOR) [Member] | Sitka AAC Note |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate | 4.50% |  |  |  |
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Interest Rate on Ambac Note Post Exit From Rehabilitation | 1.00% |  |  |  |
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] | Sitka AAC Note |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate | 0.75% |  |  |  |
Long-term Debt [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Gain Contingency, Unrecorded Amount | $ 1,400 |  |  |  |

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