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Fair Value Of Financial Instruments (Quantitative Information Regarding The Significant Unobservable Inputs For Certain Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Detail) - USD ($)
$ in Millions

Jun. 30, 2020

Dec. 31, 2019

Cash Flows [Member] | Other Derivatives Liabilities [Member] | Discounted cash flow [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Fair value, liabilities

$ 37

$ 34

Cash Flows [Member] | Other Derivatives Liabilities [Member] | Minimum [Member] | Discounted cash flow [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Range percentage

^[1]

0.00%

0.00%

Cash Flows [Member] | Other Derivatives Liabilities [Member] | Maximum [Member] | Discounted cash flow [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Range percentage

^[1]

49.00%

49.00%

Cash Flows [Member] | Other Derivatives Liabilities [Member] | Weighted Average [Member] | Discounted cash flow [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Range percentage

^[1]

25.00%

25.00%

Credit Derivatives [Member] | Nonperformance Risk [Member] | Commercial Mortgage Backed Securities [Member] | Direct Price Model [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Fair value, liabilities

$ 8

$ 7

Credit Derivatives [Member] | Nonperformance Risk [Member] | Commercial Mortgage Backed Securities [Member] | Minimum [Member] | Direct Price Model [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Range percentage

54.00%

54.00%

Credit Derivatives [Member] | Nonperformance Risk [Member] | Commercial Mortgage Backed Securities [Member] | Maximum [Member] | Direct Price Model [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Range percentage

54.00%

54.00%

Credit Derivatives [Member] | Nonperformance Risk [Member] | Commercial Mortgage Backed Securities [Member] | Weighted Average [Member] | Direct Price Model [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Range percentage

(54.00%)

(54.00%)

Loans Receivable and Other Instruments at Fair Value [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Market Prices Adjusted For Financial Guarantees Provided To Vie Obligations [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Fair Value, assets

$ 116

$ 136

Loans Receivable and Other Instruments at Fair Value [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Minimum [Member] | Market Prices Adjusted For Financial Guarantees Provided To Vie Obligations [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Range percentage

(30.00%)

^[2]

(20.00%)

Loans Receivable and Other Instruments at Fair Value [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Maximum [Member] | Market Prices Adjusted For Financial Guarantees Provided To Vie Obligations [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Range percentage

106.00%

^[2]

99.00%

Loans Receivable and Other Instruments at Fair Value [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Weighted Average [Member] | Market Prices Adjusted For Financial Guarantees Provided To Vie Obligations [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Range percentage

(14.00%)

^[2]

(22.00%)

Loan Repurchase Commitments [Member] | Variable Interest Entity Primary Beneficiary [Member] | Recovery Rates And Breach Rates [Member] | Discounted cash flow [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Fair Value, assets

$ 524

$ 486

Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Quoted market prices of VIE assets adjusted for financial guarantees provided [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Fair value, liabilities

$ 291

$ 347

Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Minimum [Member] | Quoted market prices of VIE assets adjusted for financial guarantees provided [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Range percentage

31.00%

^[2]

37.00%

Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Maximum [Member] | Quoted market prices of VIE assets adjusted for financial guarantees provided [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Range percentage

72.00%

^[2]

76.00%

Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] | Impact Of Financial Guarantee [Member] | Weighted Average [Member] | Quoted market prices of VIE assets adjusted for financial guarantees provided [Member]

Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]

Range percentage

(58.00%)

^[2]

(61.00%)

[1]	Midpoint of cash flows are used for the weighted average.
[2]	Weighted average represents the total MBIA guarantees as a percentage of total instrument fair value.

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- Definition

This element represents the fair value measurement range percentage of the Company's assets and liabilities measured at fair value.

+ References

No definition available.

+ Details

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- Definition

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+ References

No definition available.

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- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- Definition

Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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