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Background and Basis of Presentation - Surplus Note Exchange (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Insurance [Line Items] |  |  |
Net realized gains on extinguishment of debt | $ 0 | $ 81 | $ 33
Realized Investment Gains (Losses) | (22) | 31 | 7
Parent Company [Member] |  |  |
Insurance [Line Items] |  |  |
Realized Investment Gains (Losses) | $ 0 | (14) | $ (5)
5.1% Surplus Notes, General Account, Due 2020 [Member] |  |  |
Insurance [Line Items] |  |  |
Net realized gains on extinguishment of debt |  | $ 134 |
Ambac Assurance Corporation [Member] | 5.1 % Surplus Notes Due 2020 [Member] |  |  |
Insurance [Line Items] |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 5.10% | 5.10% |

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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
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