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Fair Value of Financial Instruments (Changes In Level 3 Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Detail) - Fair Value Inputs Level 3 [Member] - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | $ 216 |  | $ 104 |
Total gains/(losses) included in earnings, assets |  | (36) |  | 26 |
Unrealized gains/(losses) included in OCI, assets |  | 0 | [1] | 0 | [2]
Purchases, assets |  | 0 |  | 160 |
Issuances, assets |  | 0 |  | 0 |
Settlements, assets |  | (9) |  | (24) |
Sales, assets |  | (26) |  | (50) |
Transfers into level 3, assets |  | 1 |  | 0 |
Transfers out of level 3, assets |  | 0 |  | 0 |
Ending balance, fair value assets |  | 146 |  | 216 |
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | (7) |  | 5 |
Change in unrealized gains/(losses) for the period included in OCI for Assets still held, assets |  | 0 | [1] | 0 | [2]
Beginning balance, fair value liabilities |  | 219 |  | 389 |
Total (gains)/losses included in earnings, liabilities |  | 38 |  | (4) |
Unrealized (gains)/losses included in OCI, liabilities |  | (44) | [3] | 14 | [4]
Purchases, liabilities |  | 0 |  | 0 |
Issuances, liabilities |  | 62 |  | 0 |
Settlements, liabilities |  | (46) |  | (180) |
Sales, liabilities |  | (97) |  | 0 |
Transfers into Level 3, liabilities |  | 0 |  | 0 |
Transfers out of Level 3, liabilities |  | 0 |  | 0 |
Ending balance, fair value liabilities |  | 132 |  | 219 |
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | 15 |  | (27) |
Change in Unrealized Gains/ (Losses) for the Period Included in OCI for Liabilities still held |  | $ (4) | [3] | $ 31 | [4]
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] |  | Other Income |  | Other Income |
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] |  | Other Income |  | Other Income |
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Liability, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration] |  | Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Unrealized Gain (Loss) Arising During Period, before Tax |  |  |
Loans receivable - residential [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | $ 78 |  | $ 77 |
Total gains/(losses) included in earnings, assets |  | (33) |  | 10 |
Unrealized gains/(losses) included in OCI, assets |  | 0 | [1] | 0 | [2]
Purchases, assets |  | 0 |  | 0 |
Issuances, assets |  | 0 |  | 0 |
Settlements, assets |  | (9) |  | (9) |
Sales, assets |  | (1) |  | 0 |
Transfers into level 3, assets |  | 0 |  | 0 |
Transfers out of level 3, assets |  | 0 |  | 0 |
Ending balance, fair value assets |  | 35 |  | 78 |
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | 1 |  | 5 |
Change in unrealized gains/(losses) for the period included in OCI for Assets still held, assets |  | 0 | [1] | 0 | [2]
Residential Mortgage-Backed Non Agency [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 0 |  | 0 |
Total gains/(losses) included in earnings, assets |  |  |  | 2 |
Unrealized gains/(losses) included in OCI, assets | [2] |  |  | 0 |
Purchases, assets |  |  |  | 59 |
Issuances, assets |  |  |  | 0 |
Settlements, assets |  |  |  | (11) |
Sales, assets |  |  |  | (50) |
Transfers into level 3, assets |  |  |  | 0 |
Transfers out of level 3, assets |  |  |  | 0 |
Ending balance, fair value assets |  |  |  | 0 |
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  |  |  | 0 |
Change in unrealized gains/(losses) for the period included in OCI for Assets still held, assets | [2] |  |  | 0 |
Corporate Obligations [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 0 |  |  |
Total gains/(losses) included in earnings, assets |  | 0 |  |  |
Unrealized gains/(losses) included in OCI, assets | [1] | 0 |  |  |
Purchases, assets |  | 0 |  |  |
Issuances, assets |  | 0 |  |  |
Settlements, assets |  | 0 |  |  |
Sales, assets |  | 0 |  |  |
Transfers into level 3, assets |  | 1 |  |  |
Transfers out of level 3, assets |  | 0 |  |  |
Ending balance, fair value assets |  | 1 |  | 0 |
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | 0 |  |  |
Change in unrealized gains/(losses) for the period included in OCI for Assets still held, assets | [1] | 0 |  |  |
Equity investments [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 115 |  | 0 |
Total gains/(losses) included in earnings, assets |  | (7) |  | 14 |
Unrealized gains/(losses) included in OCI, assets |  | 0 | [1] | 0 | [2]
Purchases, assets |  | 0 |  | 101 |
Issuances, assets |  | 0 |  | 0 |
Settlements, assets |  | 0 |  | 0 |
Sales, assets |  | 0 |  | 0 |
Transfers into level 3, assets |  | 0 |  | 0 |
Transfers out of level 3, assets |  | 0 |  | 0 |
Ending balance, fair value assets |  | 108 |  | 115 |
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | (7) |  | 0 |
Change in unrealized gains/(losses) for the period included in OCI for Assets still held, assets |  | 0 | [1] | 0 | [2]
Collateralized Debt Obligations [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 0 |  | 4 |
Total gains/(losses) included in earnings, assets |  |  |  | 0 |
Unrealized gains/(losses) included in OCI, assets | [2] |  |  | 0 |
Purchases, assets |  |  |  | 0 |
Issuances, assets |  |  |  | 0 |
Settlements, assets |  |  |  | (4) |
Sales, assets |  |  |  | 0 |
Transfers into level 3, assets |  |  |  | 0 |
Transfers out of level 3, assets |  |  |  | 0 |
Ending balance, fair value assets |  |  |  | 0 |
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  |  |  | 0 |
Change in unrealized gains/(losses) for the period included in OCI for Assets still held, assets | [2] |  |  | 0 |
Medium Term Notes [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value liabilities |  | 41 |  | 98 |
Total (gains)/losses included in earnings, liabilities |  | 5 |  | (24) |
Unrealized (gains)/losses included in OCI, liabilities |  | (6) | [3] | 16 | [4]
Purchases, liabilities |  | 0 |  | 0 |
Issuances, liabilities |  | 0 |  | 0 |
Settlements, liabilities |  | 0 |  | (49) |
Sales, liabilities |  | 0 |  | 0 |
Transfers into Level 3, liabilities |  | 0 |  | 0 |
Transfers out of Level 3, liabilities |  | 0 |  | 0 |
Ending balance, fair value liabilities |  | 40 |  | 41 |
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | 5 |  | (23) |
Change in Unrealized Gains/ (Losses) for the Period Included in OCI for Liabilities still held |  | (6) | [3] | $ 17 | [4]
Variable Interest Entity Notes [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Liability, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration] |  |  |  | Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Unrealized Gain (Loss) Arising During Period, before Tax |
Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value liabilities |  | 172 |  | $ 291 |
Total (gains)/losses included in earnings, liabilities |  | 25 |  | 14 |
Unrealized (gains)/losses included in OCI, liabilities |  | (38) | [3] | (2) | [4]
Purchases, liabilities |  | 0 |  | 0 |
Issuances, liabilities |  | 62 |  | 0 |
Settlements, liabilities |  | (46) |  | (131) |
Sales, liabilities |  | (97) |  | 0 |
Transfers into Level 3, liabilities |  | 0 |  | 0 |
Transfers out of Level 3, liabilities |  | 0 |  | 0 |
Ending balance, fair value liabilities |  | 78 |  | 172 |
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | 2 |  | (10) |
Change in Unrealized Gains/ (Losses) for the Period Included in OCI for Liabilities still held |  | 2 | [3] | 14 | [4]
Currency Derivatives [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 0 |  | 9 |
Total gains/(losses) included in earnings, assets |  |  |  | (9) |
Unrealized gains/(losses) included in OCI, assets | [2] |  |  | 0 |
Purchases, assets |  |  |  | 0 |
Issuances, assets |  |  |  | 0 |
Settlements, assets |  |  |  | 0 |
Sales, assets |  |  |  | 0 |
Transfers into level 3, assets |  |  |  | 0 |
Transfers out of level 3, assets |  |  |  | 0 |
Ending balance, fair value assets |  |  |  | 0 |
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  |  |  | (9) |
Change in unrealized gains/(losses) for the period included in OCI for Assets still held, assets | [2] |  |  | 0 |
Beginning balance, fair value liabilities |  | 6 |  | 0 |
Total (gains)/losses included in earnings, liabilities |  | 8 |  | 6 |
Unrealized (gains)/losses included in OCI, liabilities |  | 0 | [3] | 0 | [4]
Purchases, liabilities |  | 0 |  | 0 |
Issuances, liabilities |  | 0 |  | 0 |
Settlements, liabilities |  | 0 |  | 0 |
Sales, liabilities |  | 0 |  | 0 |
Transfers into Level 3, liabilities |  | 0 |  | 0 |
Transfers out of Level 3, liabilities |  | 0 |  | 0 |
Ending balance, fair value liabilities |  | 14 |  | 6 |
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | 8 |  | 6 |
Change in Unrealized Gains/ (Losses) for the Period Included in OCI for Liabilities still held |  | 0 | [3] | 0 | [4]
Other Assets [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 23 |  | 14 |
Total gains/(losses) included in earnings, assets |  | 4 |  | 9 |
Unrealized gains/(losses) included in OCI, assets |  | 0 | [1] | 0 | [2]
Purchases, assets |  | 0 |  | 0 |
Issuances, assets |  | 0 |  | 0 |
Settlements, assets |  | 0 |  | 0 |
Sales, assets |  | (25) |  | 0 |
Transfers into level 3, assets |  | 0 |  | 0 |
Transfers out of level 3, assets |  | 0 |  | 0 |
Ending balance, fair value assets |  | 2 |  | 23 |
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | (1) |  | 9 |
Change in unrealized gains/(losses) for the period included in OCI for Assets still held, assets |  | $ 0 | [1] | $ 0 | [2]
[1] | Reported within the "Unrealized gains (losses) on available-for-sale securities" on MBIA's Consolidated Statement of Comprehensive Income/Loss.
[2] | Reported within the "Unrealized gains (losses) on available-for-sale securities" on MBIA's Consolidated Statement of Comprehensive Income/Loss.
[3] | Reported within the "Instrument-specific credit risk of liabilities measured at fair value" on MBIA's Consolidated Statement of Comprehensive Income/Loss.
[4] | Reported within the "Instrument-specific credit risk of liabilities measured at fair value" on MBIA's Consolidated Statement of Comprehensive Income/Loss.

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- Definition Amount of gain (loss) recognized in income from liability measured at fair value on recurring basis using unobservable input (level 3). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 + Details
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- Definition Amount of gain (loss) recognized in other comprehensive income (OCI) from liability measured at fair value on recurring basis using unobservable input (level 3). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(1a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 + Details
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