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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) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021
Accounts Notes And Loans Receivable [Line Items] |  |  |
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] |  |  | Net Gains Losses On Financial Instruments At Fair Value And Foreign Exchange
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] |  |  | Net Gains Losses On Financial Instruments At Fair Value And Foreign Exchange
Fair Value Inputs Level 3 [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value assets |  | $ 104 | $ 744
Total gains/(losses) included in earnings, assets |  | 26 | 31
Unrealized gains/(losses) included in OCI, assets | [1] | 0 | 0
Purchases, assets |  | 160 | 0
Issuances, assets |  | 0 | 0
Settlements, assets |  | (24) | (619)
Sales, assets |  | (50) | (60)
Transfers into level 3, assets |  | 0 | 8
Transfers out of level 3, assets |  | 0 | 0
Ending balance, fair value assets |  | 216 | 104
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | 5 | 24
Change in unrealized gains/(losses) for the period included in OCI for Liabilities still held | [1] | 0 | 0
Beginning balance, fair value liabilities |  | 389 | 462
Total (gains)/losses included in earnings, liabilities |  | (4) | 29
Unrealized (gains)/losses included in OCI, liabilities | [2] | 14 | (5)
Purchases, liabilities |  | 0 | 0
Issuances, liabilities |  | 0 | 0
Settlements, liabilities |  | (180) | (92)
Sales, liabilities |  | 0 | (5)
Transfers into Level 3, liabilities |  | 0 | 0
Transfers out of Level 3, liabilities |  | 0 | 0
Ending balance, fair value liabilities |  | 219 | 389
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | (27) | 7
Change in Unrealized Gains/ (Losses) for the Period Included in OCI for Liabilities still held | [2] | 31 | 15
Loans receivable - residential [Member] | Variable Interest Entity Primary Beneficiary [Member] | Fair Value Inputs Level 3 [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value assets |  | 77 | 120
Total gains/(losses) included in earnings, assets |  | 10 | 32
Unrealized gains/(losses) included in OCI, assets | [1] | 0 | 0
Purchases, assets |  | 0 | 0
Issuances, assets |  | 0 | 0
Settlements, assets |  | (9) | (15)
Sales, assets |  | 0 | (60)
Transfers into level 3, assets |  | 0 | 0
Transfers out of level 3, assets |  | 0 | 0
Ending balance, fair value assets |  | 78 | 77
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | 5 | 21
Change in unrealized gains/(losses) for the period included in OCI for Liabilities still held | [1] | 0 | 0
Loan Repurchase Commitments [Member] | Variable Interest Entity Primary Beneficiary [Member] | Fair Value Inputs Level 3 [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value assets |  | 0 | 604
Total gains/(losses) included in earnings, assets |  |  | (4)
Unrealized gains/(losses) included in OCI, assets | [1] |  | 0
Purchases, assets |  |  | 0
Issuances, assets |  |  | 0
Settlements, assets |  |  | (600)
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 Liabilities still held | [1] |  | 0
Residential Mortgage-Backed Non-Agency [Member] | Fair Value Inputs Level 3 [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value assets |  | 0 |
Total gains/(losses) included in earnings, assets |  | 2 |
Unrealized gains/(losses) included in OCI, assets | [1] | 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 | 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 Liabilities still held | [1] | 0 |
Commercial Mortgage-Backed [Member] | Variable Interest Entity Primary Beneficiary [Member] | Fair Value Inputs Level 3 [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value assets |  | 0 | 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 |  |  | (4)
Sales, assets |  |  | 0
Transfers into level 3, assets |  |  | 4
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 Liabilities still held | [1] |  | 0
Collateralized Debt Obligations [Member] | Variable Interest Entity Primary Beneficiary [Member] | Fair Value Inputs Level 3 [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value assets |  | 4 | 0
Total gains/(losses) included in earnings, assets |  | 0 | 0
Unrealized gains/(losses) included in OCI, assets | [1] | 0 | 0
Purchases, assets |  | 0 | 0
Issuances, assets |  | 0 | 0
Settlements, assets |  | (4) | 0
Sales, assets |  | 0 | 0
Transfers into level 3, assets |  | 0 | 4
Transfers out of level 3, assets |  | 0 | 0
Ending balance, fair value assets |  | 0 | 4
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | 0 | 0
Change in unrealized gains/(losses) for the period included in OCI for Liabilities still held | [1] | 0 | 0
Medium Term Notes [Member] | Fair Value Inputs Level 3 [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value liabilities |  | 98 | 110
Total (gains)/losses included in earnings, liabilities |  | (24) | (17)
Unrealized (gains)/losses included in OCI, liabilities | [2] | 16 | 10
Purchases, liabilities |  | 0 | 0
Issuances, liabilities |  | 0 | 0
Settlements, liabilities |  | (49) | (5)
Sales, liabilities |  | 0 | 0
Transfers into Level 3, liabilities |  | 0 | 0
Transfers out of Level 3, liabilities |  | 0 | 0
Ending balance, fair value liabilities |  | 41 | 98
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | (23) | (17)
Change in Unrealized Gains/ (Losses) for the Period Included in OCI for Liabilities still held | [2] | 17 | 10
Other Derivatives Liabilities [Member] | Fair Value Inputs Level 3 [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value liabilities |  | 0 | 49
Total (gains)/losses included in earnings, liabilities |  |  | 0
Unrealized (gains)/losses included in OCI, liabilities | [2] |  | 0
Purchases, liabilities |  |  | 0
Issuances, liabilities |  |  | 0
Settlements, liabilities |  |  | (49)
Sales, liabilities |  |  | 0
Transfers into Level 3, liabilities |  |  | 0
Transfers out of Level 3, liabilities |  |  | 0
Ending balance, fair value liabilities |  |  | 0
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  |  | 0
Change in Unrealized Gains/ (Losses) for the Period Included in OCI for Liabilities still held | [2] |  | 0
Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] | Fair Value Inputs Level 3 [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value liabilities |  | 291 | 303
Total (gains)/losses included in earnings, liabilities |  | 14 | 46
Unrealized (gains)/losses included in OCI, liabilities | [2] | (2) | (15)
Purchases, liabilities |  | 0 | 0
Issuances, liabilities |  | 0 | 0
Settlements, liabilities |  | (131) | (38)
Sales, liabilities |  | 0 | (5)
Transfers into Level 3, liabilities |  | 0 | 0
Transfers out of Level 3, liabilities |  | 0 | 0
Ending balance, fair value liabilities |  | 172 | 291
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | (10) | 24
Change in Unrealized Gains/ (Losses) for the Period Included in OCI for Liabilities still held | [2] | 14 | 5
Currency Derivatives [Member] | Variable Interest Entity Primary Beneficiary [Member] | Fair Value Inputs Level 3 [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value assets |  | 9 | 6
Total gains/(losses) included in earnings, assets |  | (9) | 3
Unrealized gains/(losses) included in OCI, assets | [1] | 0 | 0
Purchases, assets |  | 0 | 0
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 |  | 0 | 9
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | (9) | 3
Change in unrealized gains/(losses) for the period included in OCI for Liabilities still held | [1] | 0 | 0
Beginning balance, fair value liabilities |  | 0 |
Total (gains)/losses included in earnings, liabilities |  | 6 |
Unrealized (gains)/losses included in OCI, liabilities | [2] | 0 |
Purchases, liabilities |  | 0 |
Issuances, liabilities |  | 0 |
Settlements, liabilities |  | 0 |
Sales, liabilities |  | 0 |
Transfers into Level 3, liabilities |  | 0 |
Transfers out of Level 3, liabilities |  | 0 |
Ending balance, fair value liabilities |  | 6 | 0
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | 6 |
Change in Unrealized Gains/ (Losses) for the Period Included in OCI for Liabilities still held | [2] | 0 |
Other Assets [Member] | Variable Interest Entity Primary Beneficiary [Member] | Fair Value Inputs Level 3 [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value assets |  | 14 | 14
Total gains/(losses) included in earnings, assets |  | 9 | 0
Unrealized gains/(losses) included in OCI, assets | [1] | 0 | 0
Purchases, assets |  | 0 | 0
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 |  | 23 | 14
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | 9 | 0
Change in unrealized gains/(losses) for the period included in OCI for Liabilities still held | [1] | 0 | 0
Equity investments [Member] | Fair Value Inputs Level 3 [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value assets |  | 0 |
Total gains/(losses) included in earnings, assets |  | 14 |
Unrealized gains/(losses) included in OCI, assets | [1] | 0 |
Purchases, assets |  | 101 |
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 |  | 115 | $ 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 Liabilities still held | [1] | $ 0 |
[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 “Instrument-specific credit risk of liabilities measured at fair value” on MBIA’s Consolidated Statement of Comprehensive Income/Loss.

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