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Insurance in Force (Narrative) (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Guarantor Obligations [Line Items] |  |  |
Transactions guaranteed by MBIA on behalf of affiliated companies | $ 2,200 |  |
Aggregate amount of insurance in force ceded to reinsurers | 5,100 | $ 7,600 |
Aggregate amount of insured par outstanding ceded to reinsurers | 2,724 | 4,200 |
Recoveries received on claims for financial guarantee policies under reinsurance contracts | 4 | 12 |
Ceding commissions from reinsurance | 1 | 1 | $ 1
Insurance in Force | 154,900 | 235,900 |
Gross Par Amount | 87,000 | 141,200 |
U S Public Finance Insurance [Member] |  |  |
Guarantor Obligations [Line Items] |  |  |
Aggregate amount of insured par outstanding ceded to reinsurers | 2,100 |  |
Structured Finance And International Insurance [Member] |  |  |
Guarantor Obligations [Line Items] |  |  |
Aggregate amount of insured par outstanding ceded to reinsurers | $ 593 |  |
MBIA UK [Member] |  |  |
Guarantor Obligations [Line Items] |  |  |
Aggregate amount of insurance in force ceded to reinsurers |  | 267 |
Insurance in Force |  | 18,600 |
Gross Par Amount |  | $ 12,000 |
Minimum [Member] |  |  |
Guarantor Obligations [Line Items] |  |  |
Insurance in force, expected maturity range, years | 1 year |  |
Minimum [Member] | Investment agreements, MTNs and other affiliated contracts [Member] |  |  |
Guarantor Obligations [Line Items] |  |  |
Future guarantee payments, maturity range, (years) | 1 year |  |
Maximum [Member] |  |  |
Guarantor Obligations [Line Items] |  |  |
Insurance in force, expected maturity range, years | 40 years |  |
Maximum [Member] | Investment agreements, MTNs and other affiliated contracts [Member] |  |  |
Guarantor Obligations [Line Items] |  |  |
Future guarantee payments, maturity range, (years) | 20 years |  |

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