XML 73 R60.htm IDEA: XBRL DOCUMENT
v3.3.0.814

Investments (Credit Ratings Of Asset-Backed And Mortgage-Backed Securities And Corporate Obligations In Available-For-Sale Investments For Which Fair Value Was Less Than Amortized Cost) (Detail) - USD ($) $ in Millions | Sep. 30, 2015 | Dec. 31, 2014
--- | --- | ---
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | $ 2,019 | $ 2,071
Asset-backed [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 307 |
Gross unrealized losses | (30) |
Mortgage-backed [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 495 |
Gross unrealized losses | (10) |
Corporate Obligations [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 610 |
Gross unrealized losses | (104) |
Total ABS MBS and Corporate Obligations [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 1,412 |
Gross unrealized losses | (144) |
Moody's Aaa [Member] | Asset-backed [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 153 |
Gross unrealized losses | (1) |
Moody's Aaa [Member] | Mortgage-backed [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 446 |
Gross unrealized losses | (4) |
Moody's Aaa [Member] | Corporate Obligations [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 78 |
Gross unrealized losses | (1) |
Moody's Aaa [Member] | Total ABS MBS and Corporate Obligations [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 677 |
Gross unrealized losses | (6) |
Moodys Aa 1 Rating [Member] | Asset-backed [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 88 |
Gross unrealized losses | (1) |
Moodys Aa 1 Rating [Member] | Mortgage-backed [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 2 |
Gross unrealized losses | 0 |
Moodys Aa 1 Rating [Member] | Corporate Obligations [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 179 |
Gross unrealized losses | (3) |
Moodys Aa 1 Rating [Member] | Total ABS MBS and Corporate Obligations [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 269 |
Gross unrealized losses | (4) |
Moody's A1 [Member] | Asset-backed [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 1 |
Gross unrealized losses | 0 |
Moody's A1 [Member] | Mortgage-backed [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 3 |
Gross unrealized losses | 0 |
Moody's A1 [Member] | Corporate Obligations [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 260 |
Gross unrealized losses | (4) |
Moody's A1 [Member] | Total ABS MBS and Corporate Obligations [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 264 |
Gross unrealized losses | (4) |
Moody's Baa 1 Rating [Member] | Asset-backed [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 2 |
Gross unrealized losses | 0 |
Moody's Baa 1 Rating [Member] | Mortgage-backed [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 5 |
Gross unrealized losses | 0 |
Moody's Baa 1 Rating [Member] | Corporate Obligations [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 71 |
Gross unrealized losses | (6) |
Moody's Baa 1 Rating [Member] | Total ABS MBS and Corporate Obligations [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 78 |
Gross unrealized losses | (6) |
Below Investment Grade [Member] | Asset-backed [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 62 |
Gross unrealized losses | (28) |
Below Investment Grade [Member] | Mortgage-backed [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 26 |
Gross unrealized losses | (2) |
Below Investment Grade [Member] | Corporate Obligations [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 8 |
Gross unrealized losses | 0 |
Below Investment Grade [Member] | Total ABS MBS and Corporate Obligations [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 96 |
Gross unrealized losses | (30) |
Not Rated [Member] | Asset-backed [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 1 |
Gross unrealized losses | 0 |
Not Rated [Member] | Mortgage-backed [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 13 |
Gross unrealized losses | (4) |
Not Rated [Member] | Corporate Obligations [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 14 |
Gross unrealized losses | (90) |
Not Rated [Member] | Total ABS MBS and Corporate Obligations [Member] |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Fair value | 28 |
Gross unrealized losses | $ (94) |

X
- Definition Amount of accumulated pre-tax unrealized losses before deducting pre-tax unrealized gains on investments in available-for-sale securities impacting investments. + References No definition available. + Details
Name: | mbi_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInInvestments
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
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_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_MortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=mbi_AbsMbsCorporateObligationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditRatingMoodysAxis=us-gaap_MoodysAaaRatingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditRatingMoodysAxis=us-gaap_MoodysAa1RatingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditRatingMoodysAxis=us-gaap_MoodysA1RatingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditRatingMoodysAxis=us-gaap_MoodysBaa1RatingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditRatingMoodysAxis=mbi_BelowInvestmentGradeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditRatingMoodysAxis=mbi_NotRatedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |