XML 58 R47.htm IDEA: XBRL DOCUMENT
v3.5.0.2

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 | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2016 | Jun. 30, 2015 | Jun. 30, 2016 | Jun. 30, 2015
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | $ 1,850 | $ 2,122 | $ 1,834 | $ 2,097
Realized gains/(losses), assets |  | 0 | 0 | (1) | (2)
Unrealized gains/(losses) included in earnings, assets |  | (9) | (4) | (38) | 7
Unrealized gains/(losses) included in OCI, assets |  | 19 | 3 | 25 | 2
Foreign exchange recognized in OCI or earnings, assets |  | 0 | 2 | 0 | 3
Purchases, assets |  | 127 | 0 | 272 | 112
Issuances, assets |  | 0 | 0 | 0 | 0
Settlements, assets |  | (77) | (76) | (177) | (144)
Sales, assets |  | (107) | 0 | (107) | (16)
Transfers into level 3, assets | [1] | 4 | 23 | 9 | 23
Transfers out of level 3, assets | [1] | 0 | (24) | (10) | (36)
Ending balance, fair value assets |  | 1,807 | 2,046 | 1,807 | 2,046
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | (9) | (1) | (27) | 10
Beginning balance, fair value liabilities |  | 1,459 | 1,795 | 1,531 | 1,200
Realized gains/(losses), liabilities |  | 2 | 3 | 16 | 12
Unrealized gains/(losses included in earnings, liabilities |  | (15) | (71) | (26) | (97)
Unrealized gains/(losses) included in OCI, liabilities |  | 0 | 0 | 0 | 0
Foreign exchange recognized in OCI or earnings, liabilities |  | (4) | 7 | 4 | (16)
Purchases, liabilities |  | 0 | 0 | 9 | 695
Issuances, liabilities |  | 0 | 0 | 0 | 0
Settlements, liabilities |  | (2) | (29) | (94) | (89)
Sales, liabilities |  | (631) | 0 | (631) | 0
Transfers into Level 3, liabilities | [1] | 0 | 0 | 0 | 0
Transfers out of Level 3, liabilities | [1] | 0 | 0 | 0 | 0
Ending balance, fair value liabilities |  | 809 | 1,705 | 809 | 1,705
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | (19) | (54) | (20) | (101)
Residential Prime Financing Receivable [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 1,115 | 1,372 | 1,185 | 1,431
Unrealized gains/(losses) included in earnings, assets |  | (16) |  | (30) | (3)
Settlements, assets |  | (54) | (54) | (110) | (110)
Ending balance, fair value assets |  | 1,045 | 1,318 | 1,045 | 1,318
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | (16) |  | (30) | (3)
Other Loans Receivable [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 253 | 108 | 107 |
Unrealized gains/(losses) included in earnings, assets |  | 1 |  | 1 |
Purchases, assets |  |  |  | 146 | 108
Sales, assets |  | (107) |  | (107) |
Ending balance, fair value assets |  | 147 | 108 | 147 | 108
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | 1 |  | 1 |
Loan Repurchase Commitments [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 399 | 385 | 396 | 379
Unrealized gains/(losses) included in earnings, assets |  | 2 | 3 | 5 | 9
Ending balance, fair value assets |  | 401 | 388 | 401 | 388
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | 2 | 3 | 5 | 9
State and municipal bonds [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 3 | 6 | 41 | 8
Purchases, assets |  | 121 |  | 121 |
Settlements, assets |  |  | (1) | (38) | (1)
Transfers out of level 3, assets | [1] |  |  |  | (2)
Ending balance, fair value assets |  | 124 | 5 | 124 | 5
Foreign Government Debt [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 2 | 6 | 2 | 6
Purchases, assets |  | 5 |  | 5 |
Settlements, assets |  |  | (1) |  | (1)
Ending balance, fair value assets |  | 7 | 5 | 7 | 5
Corporate Obligations [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 1 | 10 | 7 | 10
Purchases, assets |  | 1 |  |  |
Transfers into level 3, assets | [1] |  | 8 |  | 8
Transfers out of level 3, assets | [1] |  | (10) | (5) | (10)
Ending balance, fair value assets |  | 2 | 8 | 2 | 8
Corporate Obligations [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 1 | 53 | 11 | 55
Unrealized gains/(losses) included in earnings, assets |  |  | (1) | (5) | (1)
Settlements, assets |  |  | (3) |  | (5)
Transfers into level 3, assets | [1] | 2 |  | 2 |
Transfers out of level 3, assets | [1] |  | (14) | (5) | (14)
Ending balance, fair value assets |  | 3 | 35 | 3 | 35
Residential Mortgage Backed Non Agency [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  |  | 3 |  | 3
Unrealized gains/(losses) included in earnings, assets |  |  |  |  | 1
Settlements, assets |  |  |  |  | (1)
Transfers into level 3, assets | [1] | 1 | 2 | 1 | 2
Ending balance, fair value assets |  | 1 | 5 | 1 | 5
Commercial Mortgage Backed Securities [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  |  | 1 |  | 2
Transfers out of level 3, assets | [1] |  |  |  | (1)
Ending balance, fair value assets |  |  | 1 |  | 1
Commercial Mortgage Backed Securities [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 2 |  |  |
Transfers into level 3, assets | [1] |  |  | 2 |
Ending balance, fair value assets |  | 2 |  | 2 |
Collateralized Debt Obligations [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 26 | 74 | 29 | 87
Unrealized gains/(losses) included in OCI, assets |  | 17 | 1 | 18 | 1
Settlements, assets |  | (23) | (9) | (27) | (14)
Sales, assets |  |  |  |  | (8)
Transfers into level 3, assets | [1] |  | 1 |  | 1
Ending balance, fair value assets |  | 20 | 67 | 20 | 67
Collateralized Debt Obligations [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 1 | 4 | 1 | 5
Settlements, assets |  |  |  |  | (1)
Ending balance, fair value assets |  | 1 | 4 | 1 | 4
Other Asset Backed [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 39 | 74 | 38 | 85
Realized gains/(losses), assets |  |  |  | (1) | (2)
Unrealized gains/(losses) included in earnings, assets |  |  |  | (1) |
Unrealized gains/(losses) included in OCI, assets |  | 2 | 2 | 7 | 1
Purchases, assets |  |  |  |  | 4
Settlements, assets |  |  | (5) | (2) | (7)
Sales, assets |  |  |  |  | (8)
Transfers into level 3, assets | [1] |  | 12 |  | 12
Transfers out of level 3, assets | [1] |  |  |  | (2)
Ending balance, fair value assets |  | 41 | 83 | 41 | 83
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  |  |  | (1) |
Other Asset Backed [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 3 | 21 | 6 | 26
Unrealized gains/(losses) included in earnings, assets |  |  | (1) | (6) | 2
Settlements, assets |  |  | (3) |  | (4)
Transfers into level 3, assets | [1] | 1 |  | 4 |
Transfers out of level 3, assets | [1] |  |  |  | (7)
Ending balance, fair value assets |  | 4 | 17 | 4 | 17
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  |  | (1) |  | 2
Medium Term Notes [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value liabilities |  | 165 | 180 | 161 | 197
Unrealized gains/(losses included in earnings, liabilities |  |  | (21) | (4) | (15)
Foreign exchange recognized in OCI or earnings, liabilities |  | (4) | 7 | 4 | (16)
Ending balance, fair value liabilities |  | 161 | 166 | 161 | 166
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | (4) | (14) |  | (31)
Credit Derivatives [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value liabilities |  | 99 | 207 | 85 | 244
Realized gains/(losses), liabilities |  | 2 | 3 | 16 | 12
Unrealized gains/(losses included in earnings, liabilities |  | 5 | (63) | 19 | (100)
Settlements, liabilities |  | (2) | (3) | (16) | (12)
Ending balance, fair value liabilities |  | 104 | 144 | 104 | 144
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | 5 | (53) | 22 | (88)
Other Derivative Liabilities [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value liabilities |  | 19 | 21 | 18 | 24
Unrealized gains/(losses included in earnings, liabilities |  | 2 |  | 3 | (3)
Ending balance, fair value liabilities |  | 21 | 21 | 21 | 21
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | 2 |  | 3 | (3)
Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value liabilities |  | 1,176 | 1,387 | 1,267 | 735
Unrealized gains/(losses included in earnings, liabilities |  | (22) | 13 | (44) | 21
Purchases, liabilities |  |  |  | 9 | 695
Settlements, liabilities |  |  | (26) | (78) | (77)
Sales, liabilities |  | (631) |  | (631) |
Ending balance, fair value liabilities |  | 523 | 1,374 | 523 | 1,374
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities |  | (22) | 13 | (45) | 21
Currency Derivatives [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |  |
Accounts Notes And Loans Receivable [Line Items] |  |  |  |  |
Beginning balance, fair value assets |  | 5 | 5 | 11 |
Unrealized gains/(losses) included in earnings, assets |  | 4 | (5) | (2) | (1)
Foreign exchange recognized in OCI or earnings, assets |  |  | 2 |  | 3
Ending balance, fair value assets |  | 9 | 2 | 9 | 2
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets |  | $ 4 | $ (3) | $ (2) | $ 2
[1] | Transferred in and out at the end of the period.

X
- Definition Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis In Foreign Exchange Recognized Other Comprehensive Income or Earnings, Assets + References No definition available. + Details
Name: | mbi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisInForeignExchangeRecognizedOtherComprehensiveIncomeOrEarningsAssets
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis In Foreign Exchange Recognized Other Comprehensive Income or Earnings, Liabilities + References No definition available. + Details
Name: | mbi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisInForeignExchangeRecognizedOtherComprehensiveIncomeOrEarningsLiabilities
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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 (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those assets still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of unrealized (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those liabilities still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=36462937&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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=36462937&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 the income statement for 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=36462937&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 (loss) for 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1a) -URI http://asc.fasb.org/extlink&oid=36462937&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=36462937&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=36462937&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=36462937&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=36462937&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=36462937&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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=36462937&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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=36462937&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=36462937&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 on the income statement for 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=36462937&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 (loss) for 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1a) -URI http://asc.fasb.org/extlink&oid=36462937&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=36462937&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=36462937&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=36462937&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=36462937&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=36462937&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=36462937&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: | us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | invest_InvestmentAxis=us-gaap_ForeignGovernmentDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | invest_InvestmentAxis=mbi_CorporateObligationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | invest_InvestmentAxis=mbi_ResidentialMortgageBackedNonAgencyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

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

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

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

X
- Details
Name: | invest_InvestmentAxis=mbi_OtherDerivativeLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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