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