XML 85 R71.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Fair Value Of Financial Instruments (Aggregate Fair Value And Remaining Contractual Principal Balance Outstanding On Fair Value Option) (Detail) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Non Variable Interest Entity [Member] |  |
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items] |  |
Medium-term notes, contractual outstanding principal | $ 180 | $ 158
Medium-term notes, fair value | 115 | 101
Medium-term notes, difference | 65 | 57
Variable Interest Entity [Member] |  |
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items] |  |
Loans receivable, contractual outstanding principal | 2,296 | 1,258
Variable interest entity notes, contractual outstanding principal | 1,882 | 2,449
Loans receivable, fair value | 1,679 | 1,066
Variable interest entity notes, fair value | 1,069 | 1,351
Loans receivable, difference | 617 | 192
Variable interest entity notes, difference | 813 | 1,098
Residential Mortgage Loans [Member] | Variable Interest Entity [Member] |  |
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items] |  |
Loans receivable, contractual outstanding principal | 732 | 965
Loans receivable, 90 days or more past due, contractual outstanding principal | 170 | 143
Loans receivable, fair value | 727 | 894
Loans receivable, 90 days or more past due, fair value | 32 | 22
Loans receivable, difference | 5 | 71
Loans receivable, 90 days or more past due, difference | 138 | 121
Corporate Loans [Member] | Variable Interest Entity [Member] |  |
Schedule Of Fair Value Of Separate Accounts By Major Category Of Investment [Line Items] |  |
Loans receivable, contractual outstanding principal | 1,394 | 150
Loans receivable, fair value | 920 | 150
Loans receivable, difference | $ 474 | $ 0

X
- Definition Fair Value Option Aggregate Differences Medium Term Notes + References No definition available. + Details
Name: | mbi_FairValueOptionAggregateDifferencesMediumTermNotes
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair Value Option Aggregate Fair Value Loans Receivable + References No definition available. + Details
Name: | mbi_FairValueOptionAggregateFairValueLoansReceivable
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair Value Option Aggregate Fair Value Long Term Debt Instruments + References No definition available. + Details
Name: | mbi_FairValueOptionAggregateFairValueLongTermDebtInstruments
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair Value Option Aggregate Fair Value Medium Term Notes + References No definition available. + Details
Name: | mbi_FairValueOptionAggregateFairValueMediumTermNotes
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair Value Option Contractual Outstanding Principal Loans Receivable + References No definition available. + Details
Name: | mbi_FairValueOptionContractualOutstandingPrincipalLoansReceivable
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair Value Option Contractual Outstanding Principal Long Term Debt Instruments + References No definition available. + Details
Name: | mbi_FairValueOptionContractualOutstandingPrincipalLongTermDebtInstruments
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair Value Option Contractual Outstanding Principal Medium Term Notes + References No definition available. + Details
Name: | mbi_Fairvalueoptioncontractualoutstandingprincipalmediumtermnotes
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition This item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of loans and long-term receivables (other than securities categorized as trading, available-for-sale or held-to-maturity) that have contractual principal amounts and for which the fair value option has been elected. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612 + Details
Name: | us-gaap_FairValueOptionAggregateDifferencesLoansAndLongTermReceivables
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of long-term debt instruments that have contractual principal amounts and for which the fair value option has been elected. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612 + Details
Name: | us-gaap_FairValueOptionAggregateDifferencesLongTermDebtInstruments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition This item represents the aggregate fair value of loans held as assets that are 90 days or more past due for which the fair value option has been elected. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612 + Details
Name: | us-gaap_FairValueOptionLoansHeldAsAssets90DaysOrMorePastDue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition For loans held as assets for which the fair value option has been elected, this item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of those loans that are 90 days or more past due. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (e)(3) -URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612 + Details
Name: | us-gaap_FairValueOptionLoansHeldAsAssets90DaysOrMorePastDueAggregateDifference
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the aggregate fair value of loans held as assets that are in nonaccrual status for which the fair value option has been elected, if the entity's policy is to recognize interest income separately from other changes in fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (e)(2) -URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612 + Details
Name: | us-gaap_FairValueOptionLoansHeldAsAssetsAggregateAmountInNonaccrualStatus
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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_ScheduleOfFairValueOfSeparateAccountsByMajorCategoryOfInvestmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=us-gaap_ConsolidatedEntityExcludingVariableInterestEntitiesVIEMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_InvestmentTypeAxis=mbi_ResidentialMortgageLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=mbi_OtherLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |