Insurance Regulations And Dividends (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2012
Insurance Regulations And Dividends [Line Items]
Percentage of policyholders' surplus	10.00%
Percentage of adjusted net investment income	100.00%
Maximum percentage of notional asset swap	5.00%
MBIA Corp [Member]
Insurance Regulations And Dividends [Line Items]
Dividends from subsidiaries	$ 0
Aggregate risk limits exceeded	233,000,000
Requested contingency reserve release to surplus			1,100,000,000
Statutory net loss	494,000,000	843,000,000
Statutory capital	825,000,000	1,500,000,000
Policyholders' surplus	403,000,000
Contingency reserves	422,000,000
MBIA Corp [Member] | Minimum Surplus And Contingency Reserves [Member]
Insurance Regulations And Dividends [Line Items]
Investments in certain qualifing assets	100.00%
MBIA Corp [Member] | Loss Reserves And Unearned Premium Reserves [Member]
Insurance Regulations And Dividends [Line Items]
Investments in certain qualifing assets	50.00%
MBIA Corp [Member] | Policyholders Surplus [Member]
Insurance Regulations And Dividends [Line Items]
Statutory surplus negative impact	129,000,000
Maximum percentage of statutory admitted assets invested in subsidiaries	50.00%
MBIA Corp [Member] | Surplus [Member]
Insurance Regulations And Dividends [Line Items]
Maximum percentage of statutory admitted assets invested in subsidiaries	60.00%
National [Member]
Insurance Regulations And Dividends [Line Items]
Dividends from subsidiaries	214,000,000
Unassigned surplus	0
Statutory capital	3,300,000,000	3,200,000,000
Policyholders' surplus	2,100,000,000
Contingency reserves	1,200,000,000
Statutory net income	$ 256,000,000	$ 416,000,000