Common and Preferred Stock (Narrative) (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Fair value of warrants	$ 6	$ 33
Remaining amount available under repurchase program	$ 250	$ 88	$ 94
Treasury stock shares acquired	43,000,000	16,600,000	39,900,000
Shares repurchased under share repurchase program, average price per share	$ 7.55	$ 6.37	$ 7.6
Preferred stock shares issued	0	0
Preferred stock shares outstanding	0	0
Preferred Stock Par Or Stated Value Per Share	$ 1	$ 1
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
2014 Repurchase Authorization [Member]
Class of Stock [Line Items]
Authorized repurchase of common stock, value	$ 200
Stock repurchase program cancelled amount	61
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
2016 Repurchase Authorization [Member]
Class of Stock [Line Items]
Authorized repurchase of common stock, value	100
Stock repurchase program cancelled amount	13
June 27, 2017 Repurchase Authorization [Member]
Class of Stock [Line Items]
Authorized repurchase of common stock, value	250
November 3, 2017 Repurchase Authorization [Member]
Class of Stock [Line Items]
Authorized repurchase of common stock, value	250
Remaining amount available under repurchase program	$ 250
Unaffiliated Investors [Member] | MBIA Insurance Corporation [Member]
Class of Stock [Line Items]
Preferred stock shares outstanding	1,315
Long-Term Incentive Plan [Member]
Class of Stock [Line Items]
Treasury stock shares acquired	490,557	419,806
Warrant [Member] | HighBridge
Class of Stock [Line Items]
Warrants outstanding	9,940,000
Warrant exercise price	$ 9.59
Warrant Term	5 years
Grossup Warrant [Member] | HighBridge
Class of Stock [Line Items]
Warrants outstanding	1,910,000
Warrant exercise price	$ 9.59
Warrant Term	5 years