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Background and Business Description - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions |  | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Apr. 29, 1991 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2015 | Jul. 06, 2021 | Feb. 12, 2018 | May 01, 2013 | Apr. 30, 2013
Background And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |
Entity Incorporation, Date of Incorporation | Apr. 29, 1991 |  |  |  |  |  |  |  |
Tier 2 Note Security in RMBS Litigation Settlement Proceeds |  |  |  |  |  |  | $ 1,600 |  |
Common stock, shares authorized |  | 130,000,000 | 130,000,000 |  |  |  |  |  |
Common Stock, Par or Stated Value Per Share |  |  |  |  |  |  |  |  | $ 0.01
Preferred stock, shares authorized |  | 20,000,000 | 20,000,000 |  |  |  |  |  |
Preferred Stock, Par or Stated Value Per Share |  | $ 0.01 |  |  |  |  |  |  | $ 0.01
Common stock, shares issued |  | 46,477,068 | 45,865,081 |  |  |  |  |  |
Class of Warrant or Right, Exercise Price of Warrants or Rights |  |  |  |  |  |  |  | $ 16.67 |
Common Stock Voting Restrictions | 10.00% |  |  |  |  |  |  |  |
Common Stock Voting Restriction Less One Vote | 10.00% |  |  |  |  |  |  |  |
Common Stock Transfer Restrictions | 5.00% |  |  |  |  |  |  |  |
Common Stock Additional Transfer Restrictions |  |  |  |  | 5.00% |  |  |  |
Financial Guarantee Insurance Contracts, Accelerated Premium Revenue, Amount |  | $ 1 | $ 12 | $ 10 |  |  |  |  |
Business Acquisition, Percentage of Voting Interests Acquired |  | 80.00% |  |  |  |  |  |  |
LIBOR + 4.5% Senor Secured Notes Due 2026 | London Interbank Offered Rate (LIBOR) [Member] |  |  |  |  |  |  |  |  |
Background And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  |  | 4.50% |  |  |
LSNI Secured Notes due 2023 |  |  |  |  |  |  |  |  |
Background And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |
Repayment of Long-term Debt, Long-term Lease Obligation, and Capital Security |  | $ 1,163 |  |  |  |  |  |  |
Sitka Holdings, LLC | LIBOR + 4.5% Senor Secured Notes Due 2026 |  |  |  |  |  |  |  |  |
Background And Basis Of Presentation [Line Items] |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  | $ 1,175 |  |  |

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