Business and Risks (Narrative) (Detail) (USD $) Share data in Millions, unless otherwise specified	0 Months Ended	6 Months Ended			6 Months Ended		0 Months Ended					0 Months Ended
	May 07, 2013 numberofinstitutions	Jun. 30, 2013 segments	Jun. 30, 2013 Mbia Inc [Member]	Dec. 31, 2012 Mbia Inc [Member]	Jun. 30, 2013 Mbia Corp [Member]	Dec. 31, 2012 Mbia Corp [Member]	May 06, 2013 Bank Of America [Member]	May 07, 2013 Societe Generale [Member]	May 02, 2013 Flagstar Bank [Member]	Mar. 31, 2013 Amount Outstanding [Member]	May 06, 2013 Amount Outstanding Before Bofa Settlement [Member]	May 06, 2013 Corporate Obligations [Member] Bank Of America [Member]	May 06, 2013 Cash [Member] Bank Of America [Member]	May 06, 2013 Warrant [Member] Bank Of America [Member]	May 06, 2013 CMBS Pool Insured Gross Par [Member] Bank Of America [Member]
Business Acquisition [Line Items]
Number of operating segments		3
Proceeds from legal settlements							$ 1,700,000,000		$ 110,000,000			$ 136,000,000	$ 1,600,000,000
MBIA debt coupon rate			5.70%
Warrant Term							5 years
Stock Issued During Period Shares New Issues														9.94
Warrant exercise price														9.59
Settlement without prejudice term							1 year
Line of credit maximum amount							500,000,000
Line of credit term							3 years
National secured loan										1,700,000,000	1,600,000,000
Number of resolved Article 78 plaintiffs	18
Liquid assets			327,000,000	239,000,000	92,000,000	345,000,000
Amount released from tax escrow account			115,000,000
Commuted gross insured exposure					$ 19,900,000,000		$ 7,400,000,000	$ 4,200,000,000							$ 6,100,000,000