XML 66 R55.htm IDEA: XBRL DOCUMENT
v3.19.2

Investments (Gross Unrealized Losses Related To Available-For-Sale And Held-To-Maturity Investments) (Detail) - Fixed Maturities [Member] - USD ($) $ in Millions | Jun. 30, 2019 | Dec. 31, 2018
--- | --- | ---
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | $ 296 | $ 1,476
Less than 12 months, unrealized losses | (2) | (47)
12 months or longer, fair value | 579 | 944
12 months or longer, unrealized losses | (45) | (120)
Total available-for-sale, fair value | 875 | 2,420
Total available-for-sale, unrealized losses | (47) | (167)
U S Treasury And Government [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 118 | 231
Less than 12 months, unrealized losses | 0 | (1)
12 months or longer, fair value | 153 | 278
12 months or longer, unrealized losses | (2) | (9)
Total available-for-sale, fair value | 271 | 509
Total available-for-sale, unrealized losses | (2) | (10)
US States And Political Subdivisions [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 0 | 60
Less than 12 months, unrealized losses | 0 | (1)
12 months or longer, fair value | 57 | 135
12 months or longer, unrealized losses | (1) | (10)
Total available-for-sale, fair value | 57 | 195
Total available-for-sale, unrealized losses | (1) | (11)
Foreign Government Debt [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 3 | 5
Less than 12 months, unrealized losses | 0 | 0
12 months or longer, fair value | 0 | 2
12 months or longer, unrealized losses | 0 | 0
Total available-for-sale, fair value | 3 | 7
Total available-for-sale, unrealized losses | 0 | 0
Corporate Obligations [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 52 | 900
Less than 12 months, unrealized losses | (1) | (41)
12 months or longer, fair value | 212 | 335
12 months or longer, unrealized losses | (36) | (90)
Total available-for-sale, fair value | 264 | 1,235
Total available-for-sale, unrealized losses | (37) | (131)
Residential Mortgage Backed Agency [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 26 | 29
Less than 12 months, unrealized losses | 0 | (1)
12 months or longer, fair value | 94 | 118
12 months or longer, unrealized losses | (1) | (4)
Total available-for-sale, fair value | 120 | 147
Total available-for-sale, unrealized losses | (1) | (5)
Residential Mortgage Backed Non Agency [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 0 | 2
Less than 12 months, unrealized losses | 0 | 0
12 months or longer, fair value | 12 | 13
12 months or longer, unrealized losses | (4) | (4)
Total available-for-sale, fair value | 12 | 15
Total available-for-sale, unrealized losses | (4) | (4)
Commercial Mortgage Backed Securities [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 1 | 24
Less than 12 months, unrealized losses | 0 | 0
12 months or longer, fair value | 0 | 21
12 months or longer, unrealized losses | 0 | (2)
Total available-for-sale, fair value | 1 | 45
Total available-for-sale, unrealized losses | 0 | (2)
Collateralized Debt Obligations [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 68 | 98
Less than 12 months, unrealized losses | (1) | (3)
12 months or longer, fair value | 22 | 7
12 months or longer, unrealized losses | (1) | 0
Total available-for-sale, fair value | 90 | 105
Total available-for-sale, unrealized losses | (2) | (3)
Other Asset Backed [Member] |  |
Available For Sale Securities [Abstract] |  |
Less than 12 months, fair value | 28 | 127
Less than 12 months, unrealized losses | 0 | 0
12 months or longer, fair value | 29 | 35
12 months or longer, unrealized losses | 0 | (1)
Total available-for-sale, fair value | 57 | 162
Total available-for-sale, unrealized losses | $ 0 | $ (1)

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

X
- Definition Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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 No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for less than twelve months. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for twelve months or longer. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

X
- Details
Name: | invest_InvestmentAxis=mbi_ResidentialMortgageBackedAgencyMember
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: |