XML 161 R74.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Loss And Loss Adjustment Expense Reserves (Schedule Of Total Estimated Recoveries From Ineligible Mortgage Loans) (Details) (Ineligible Mortgage Loans [Member], USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2011 | Dec. 31, 2010
Ineligible Mortgage Loans [Member] |  |
Loss And Loss Adjustment Expense Reserves [Line Items] |  |
Total Estimated Recoveries from Ineligible loans as of Beginning Balance | $ 2,517 | $ 1,575
Accretion of Future Collections | 65 | 51
Changes in Discount Rates | 35 | 21
Recoveries (Collections) | (86) | (67)
Changes in Amount of Collections | 29 |
Changes in Assumptions | 559 | 937
Total Estimated Recoveries from Ineligible loans as of Ending Balance | $ 3,119 | $ 2,517

X
- Definition Estimated Insurance Changes In Amount Of Collections + References No definition available. + Details
Name: | mbi_EstimatedInsuranceChangesInAmountOfCollections
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Estimated Insurance Recoveries Accretion Of Future Collections + References No definition available. + Details
Name: | mbi_EstimatedInsuranceRecoveriesAccretionOfFutureCollections
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Estimated Insurance Recoveries Change In Assumptions + References No definition available. + Details
Name: | mbi_EstimatedInsuranceRecoveriesChangeInAssumptions
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Estimated Insurance Recoveries Change In Discount Rate + References No definition available. + Details
Name: | mbi_EstimatedInsuranceRecoveriesChangeInDiscountRate
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Estimated Insurance Recoveries Collections + References No definition available. + Details
Name: | mbi_EstimatedInsuranceRecoveriesCollections
Namespace Prefix: | mbi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | mbi_LossAndLossAdjustmentExpenseReservesLineItems
Namespace Prefix: | mbi_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Carrying amount as of the balance sheet date of amounts expected to be recovered under the terms of insurance contracts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 17 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.17) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_EstimatedInsuranceRecoveries
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant