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Fair Value Of Financial Instruments (Gains And Losses On Fair Value Option Included In The Company's Consolidated Statements Of Operations) (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Non Variable Interest Entity [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange |  | $ 52 | $ (17) | $ (24)
Variable Interest Entity [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange |  | 105 | 25 | 130
Investments Carried At Fair Value [Member] | Non Variable Interest Entity [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | [1] | 15 | (11) | 8
Fixed Maturity Securities Held At Fair Value - VIE [Member] | Variable Interest Entity [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | [2] | 95 | (25) | (22)
Loans Receivable and Other Instruments at Fair Value [Member] | Variable Interest Entity [Member] | Residential Mortgage Loans [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | [2] | 35 | (100) | (158)
Loans Receivable and Other Instruments at Fair Value [Member] | Variable Interest Entity [Member] | Corporate Loans and Other Instruments [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | [2] |  | 11 | 52
Loan Repurchase Commitments [Member] | Variable Interest Entity [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | [2] | 68 | 12 | 3
Other Assets [Member] | Variable Interest Entity [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | [2] | 4 |  | (3)
Medium Term Notes [Member] | Non Variable Interest Entity [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | [1] | 1 | 19 | (14)
Other Liabilities [Member] | Non Variable Interest Entity [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | [3] | (2) | (2) |
Variable Interest Entity Notes [Member] | Variable Interest Entity [Member] |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |
Net gains (losses) on financial instruments at fair value and foreign exchange | [2] | $ (89) | $ 118 | $ 230
[1] | Reported within “Net gains (losses) on financial instruments at fair value and foreign exchange” on MBIA’s consolidated statements of operations.
[2] | Reported within “Net gains (losses) on financial instruments at fair value and foreign exchange-VIE” on MBIA’s consolidated statements of operations.
[3] | Reported within “Other net realized gains (losses)” on MBIA’s consolidated statements of operations.

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