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Insurance in Force (Narrative) (Detail) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2023 | Dec. 31, 2022
Guarantor Obligations [Line Items] |  |
Transactions guaranteed by MBIA on behalf of affiliated companies | $ 1,000 |
Aggregate amount of insurance in force ceded to reinsurers | 1,700 | $ 2,000
Aggregate amount of insured par outstanding ceded to reinsurers | 782 | $ 897
US Public Finance Insurance [Member] |  |
Guarantor Obligations [Line Items] |  |
Aggregate amount of insured par outstanding ceded to reinsurers | 639 |
Structured Finance And International Insurance [Member] |  |
Guarantor Obligations [Line Items] |  |
Aggregate amount of insured par outstanding ceded to reinsurers | $ 143 |
Financial Guaranty Insurance Company [Member] |  |
Guarantor Obligations [Line Items] |  |
Financial guaranty maturity year | 2058 |
Investment agreements, MTNs and other affiliated contracts [Member] |  |
Guarantor Obligations [Line Items] |  |
Financial guaranty maturity year | 2037 |

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