Common and Preferred Stock (Narrative) (Detail) - USD ($) $ / shares in Units, $ in Millions			2 Months Ended	12 Months Ended
	Aug. 05, 2013	May. 06, 2013	Feb. 29, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2008
Class of Stock [Line Items]
Fair value of warrants				$ 18	$ 28
Treasury stock shares acquired				39,900,000	3,300,000
Treasury stock value acquired cost method				$ 303	$ 35	$ 7
Shares repurchased under share repurchase program, average price per share				$ 7.6	$ 10.45	$ 0
Remaining amount available under repurchase program				$ 94	$ 188	$ 23
Preferred stock shares issued				0	0
Preferred stock shares outstanding				0	0
Preferred Stock Par Or Stated Value Per Share				$ 1	$ 1
Blue Ridge [Member]
Class of Stock [Line Items]
Warrants outstanding		9,940,000
Warrant exercise price		$ 9.59
Preferred Stock [Member] | MBIA Insurance Corporation [Member]
Class of Stock [Line Items]
Shares repurchased under share repurchase program, average price per share				$ 10,900
Preferred stock shares issued				2,759
Preferred stock repurchased during period shares				1,444
Preferred stock, carrying value issued and outstanding				$ 28
Face value of repurchased preferred stock				10.90%
Preferred Stock Par Or Stated Value Per Share				$ 1,000
Preferred stock liquidation preference				$ 100,000
Dividend rate on preferred stock determined rate				LIBOR plus 200 basis points
2007 Repurchase Authorization [Member]
Class of Stock [Line Items]
Authorized repurchase of common stock, value				$ 1,000
2014 Repurchase Authorization [Member]
Class of Stock [Line Items]
Authorized repurchase of common stock, value				200
Remaining amount available under repurchase program				$ 61
Unaffiliated Investors [Member] | MBIA Insurance Corporation [Member]
Class of Stock [Line Items]
Preferred stock shares outstanding				1,315
July 29, 2015 Repurchase Authorization [Member]
Class of Stock [Line Items]
Authorized repurchase of common stock, value				$ 100
October 28, 2015 Repurchase Authorization [Member]
Class of Stock [Line Items]
Authorized repurchase of common stock, value				$ 100
October 28, 2015 Repurchase Authorization [Member] | SubsequentEvent [Member]
Class of Stock [Line Items]
Treasury stock shares acquired			14,900,000
Shares repurchased under share repurchase program, average price per share			$ 6.3
Long-Term Incentive Plan [Member]
Class of Stock [Line Items]
Treasury stock shares acquired				580,692	529,246
Warrant [Member] | Blue Ridge [Member]
Class of Stock [Line Items]
Warrant Term		5 years
Warrant [Member] | Warburg Pincus [Member]
Class of Stock [Line Items]
Warrants outstanding	11,800,000						11,500,000
Warrant exercise price	$ 29.44						$ 30.25
B Warrants [Member] | Warburg Pincus [Member]
Class of Stock [Line Items]
Warrants outstanding	10,100,000						9,800,000
Warrant exercise price	$ 29.44						$ 30.25
B2 Warrants [Member] | Warburg Pincus [Member]
Class of Stock [Line Items]
Warrants outstanding	4,004,945						4,000,000
Warrant exercise price	$ 16.18						$ 16.2
Grossup Warrant [Member] | Warburg Pincus [Member]
Class of Stock [Line Items]
Warrants outstanding	1,910,000
Warrant exercise price	$ 9.59
Warrant Term	5 years