XML 79 R63.htm IDEA: XBRL DOCUMENT
v3.22.0.1

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, 2021 | Dec. 31, 2020
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value assets |  | $ 744 | $ 649
Total gains/(losses) included in earnings, assets |  | 31 | 112
Unrealized gains/(losses) included in OCI, assets | [1] | 0 | 0
Purchases, assets |  | 0 | 0
Issuances, assets |  | 0 | 0
Settlements, assets |  | (619) | (17)
Sales, assets |  | (60) | 0
Transfers into level 3, assets |  | 8 | 0
Transfers out of level 3, assets |  | 0 | 0
Ending balance, fair value assets |  | 104 | 744
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | 24 | 108
Change in unrealized gains/(losses) for the period included in OCI for Liabilities still held | [1] | 0 | 0
Beginning balance, fair value liabilities |  | 462 | 500
Total (gains)/losses included in earnings, liabilities |  | 29 | 35
Unrealized (gains)/losses included in OCI, liabilities | [2] | (5) | (53)
Purchases, liabilities |  | 0 | 0
Issuances, liabilities |  | 0 | 0
Settlements, liabilities |  | (92) | (20)
Sales, liabilities |  | (5) | 0
Transfers into Level 3, liabilities |  | 0 | 0
Transfers out of Level 3, liabilities |  | 0 | 0
Ending balance, fair value liabilities |  | 389 | 462
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | 7 | 35
Change in Unrealized Gains/ (Losses) for the Period Included in OCI for Liabilities still held | [2] | 15 | (51)
Residential Prime Financing Receivable [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value assets |  | 120 | 136
Total gains/(losses) included in earnings, assets |  | 32 | 0
Unrealized gains/(losses) included in OCI, assets | [1] | 0 | 0
Purchases, assets |  | 0 | 0
Issuances, assets |  | 0 | 0
Settlements, assets |  | (15) | (16)
Sales, assets |  | (60) | 0
Transfers into level 3, assets |  | 0 | 0
Transfers out of level 3, assets |  | 0 | 0
Ending balance, fair value assets |  | 77 | 120
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | 21 | (4)
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] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value assets |  | 604 | 486
Total gains/(losses) included in earnings, assets |  | (4) | 118
Unrealized gains/(losses) included in OCI, assets | [1] | 0 | 0
Purchases, assets |  | 0 | 0
Issuances, assets |  | 0 | 0
Settlements, assets |  | (600) | 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 | 604
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | 0 | 118
Change in unrealized gains/(losses) for the period included in OCI for Liabilities still held | [1] | 0 | 0
Commercial Mortgage-Backed [Member] | Variable Interest Entity Primary Beneficiary [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 |  | (4) |
Sales, assets |  | 0 |
Transfers into level 3, assets |  | 4 |
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 |
Collateralized Debt Obligations [Member] | Variable Interest Entity Primary Beneficiary [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 |  | 4 |
Transfers out of level 3, assets |  | 0 |
Ending balance, fair value assets |  | 4 | 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 |
Other Asset Backed [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value assets |  | 0 | 1
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 |  |  | (1)
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
Medium Term Notes [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value liabilities |  | 110 | 108
Total (gains)/losses included in earnings, liabilities |  | (17) | 15
Unrealized (gains)/losses included in OCI, liabilities | [2] | 10 | (13)
Purchases, liabilities |  | 0 | 0
Issuances, liabilities |  | 0 | 0
Settlements, liabilities |  | (5) | 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 |  | 98 | 110
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | (17) | 15
Change in Unrealized Gains/ (Losses) for the Period Included in OCI for Liabilities still held | [2] | 10 | (13)
Credit Derivatives [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value liabilities |  | 0 | 7
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 |  |  | (1)
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
Other Derivatives Liabilities [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value liabilities |  | 49 | 34
Total (gains)/losses included in earnings, liabilities |  | 0 | 15
Unrealized (gains)/losses included in OCI, liabilities | [2] | 0 | 0
Purchases, liabilities |  | 0 | 0
Issuances, liabilities |  | 0 | 0
Settlements, liabilities |  | (49) | 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 |  | 0 | 49
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | 0 | 15
Change in Unrealized Gains/ (Losses) for the Period Included in OCI for Liabilities still held | [2] | 0 | 0
Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value liabilities |  | 303 | 347
Total (gains)/losses included in earnings, liabilities |  | 46 | 11
Unrealized (gains)/losses included in OCI, liabilities | [2] | (15) | (40)
Purchases, liabilities |  | 0 | 0
Issuances, liabilities |  | 0 | 0
Settlements, liabilities |  | (38) | (15)
Sales, liabilities |  | (5) | 0
Transfers into Level 3, liabilities |  | 0 | 0
Transfers out of Level 3, liabilities |  | 0 | 0
Ending balance, fair value liabilities |  | 291 | 303
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | 24 | 5
Change in Unrealized Gains/ (Losses) for the Period Included in OCI for Liabilities still held | [2] | 5 | (38)
Currency Derivatives [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value assets |  | 6 | 8
Total gains/(losses) included in earnings, assets |  | 3 | (2)
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 |  | 9 | 6
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | 3 | (2)
Change in unrealized gains/(losses) for the period included in OCI for Liabilities still held | [1] | 0 | 0
Other Assets [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value assets |  | 14 | 18
Total gains/(losses) included in earnings, assets |  | 0 | (4)
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 |  | 14 | 14
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | 0 | (4)
Change in unrealized gains/(losses) for the period included in OCI for Liabilities still held | [1] | 0 | 0
Other Payable [Member] |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |
Beginning balance, fair value liabilities |  | $ 0 | 4
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 |  |  | (4)
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
[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.

X
- 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 No definition available. + Details
Name: | us-gaap_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of unrealized gain (loss) recognized in other comprehensive income (OCI) from asset measured at fair value on recurring basis using unobservable input (level 3) and still held. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossOci
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of unrealized gain (loss) recognized in other comprehensive income (OCI) from liability measured at fair value on recurring basis using unobservable input (level 3) and still held. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueLiabilityRecurringBasisStillHeldUnrealizedGainLossOci
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of transfers of financial instrument classified as a liability into level 3 of the fair value hierarchy. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersIntoLevel3
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of transfers of financial instrument classified as a liability out of level 3 of the fair value hierarchy. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of gain (loss) recognized in other comprehensive income (OCI) from asset measured at fair value on recurring basis using unobservable input (level 3). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1a) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of issuances 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)(2) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of increase (decrease) 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=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPeriodIncreaseDecrease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of purchases 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)(2) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of sale 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)(2) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of settlement 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)(2) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- 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=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- 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 -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- 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 -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1a) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of issuances 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 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)(2) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of increase (decrease) 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 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=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPeriodIncreaseDecrease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of purchases 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 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)(2) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of sales 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 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)(2) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySales
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of settlements 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 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)(2) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- 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 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=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ConsolidatedEntitiesAxis=us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=mbi_LoanRepurchaseCommitmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CollateralizedDebtObligationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=mbi_OtherAssetBackedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_MediumTermNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=mbi_CreditDerivativesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=mbi_OtherDerivativesLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=mbi_VariableInterestEntityNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=mbi_CurrencyDerivativesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_OtherAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=mbi_OtherPayableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |