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Fair Value of Financial Instruments (Realized And Unrealized Gains And Losses Included In Earnings Pertaining To Level 3 Assets And Liabilities) (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange |  | $ 4 | $ 45 | $ 40
Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] |  | Realized Investment Gains (Losses) | Realized Investment Gains (Losses) | Realized Investment Gains (Losses)
Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange |  | $ (45) | $ (14) | $ (8)
Other net realized gains (losses) |  | (25) | 19 | (15)
Fair Value Inputs Level 3 [Member] | Total Gains (Losses) Included in Earnings [Member] |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange |  | (12) | 40 | 17
Total revenues |  | (74) | 30 | 2
Fair Value Inputs Level 3 [Member] | Change in Unrealized Gains (Losses) for the Period Included in Earnings for Assets and Liabilities still held [Member] |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange |  | (12) | 23 | 17
Total revenues |  | (22) | 32 | 17
Fair Value Inputs Level 3 [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Total Gains (Losses) Included in Earnings [Member] |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | [1] | (62) | (10) | (15)
Fair Value Inputs Level 3 [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Change in Unrealized Gains (Losses) for the Period Included in Earnings for Assets and Liabilities still held [Member] |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | [1] | $ (10) | $ 9 | $ 0
[1] | Reported within "Net gains (losses) on financial instruments at fair value and foreign exchange-VIE" and "Other net realized gains (losses)-VIE" on MBIA's consolidated statements of operations.

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-3 + Details
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