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Insurance Regulatory Restrictions Additional Details (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020
Average Annual Rate Of Return | 5.28% | 4.56%
Prescribed Discount Rate Percentage | 5.10% |
Minimum [Member] |  |
Settlement Agreement Annual Restricted Payment Amount | $ 5 |
Maximum [Member] |  |
Settlement Agreement Annual Restricted Payment Amount | 8 |
Ambac Assurance [Member] |  |
Statutory Accounting Practices, Statutory Capital and Surplus, Balance | 757 | $ 865
Ambac Assurance [Member] | Prescribed Or Permitted Additional Accounting Practices [Member] |  |
Statutory Accounting Practices, Prescribed Practice, Amount | (5) | 40
Everspan Indemnity |  |
Statutory Accounting Practices, Statutory Capital and Surplus, Balance | $ 106 | 26
Everspan Indemnity | Prescribed Or Permitted Additional Accounting Practices [Member] |  |
Statutory Accounting Practices, Prescribed Practice, Amount |  | $ 18

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