Earnings Per Share (Revised Basic And Diluted Earnings Per Share) (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended						3 Months Ended			6 Months Ended	9 Months Ended	12 Months Ended		3 Months Ended			6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011		Sep. 30, 2013 Previously reported [Member]	Jun. 30, 2013 Previously reported [Member]	Mar. 31, 2013 Previously reported [Member]	Jun. 30, 2013 Previously reported [Member]	Sep. 30, 2013 Previously reported [Member]	Dec. 31, 2012 Previously reported [Member]	Dec. 31, 2011 Previously reported [Member]	Sep. 30, 2013 Revised [Member]	Jun. 30, 2013 Revised [Member]	Mar. 31, 2013 Revised [Member]	Jun. 30, 2013 Revised [Member]	Sep. 30, 2013 Revised [Member]	Dec. 31, 2012 Revised [Member]	Dec. 31, 2011 Revised [Member]
Numerator: [Abstract]
Net income (loss) available to common shareholders - basic and diluted, as reported	$ 250		$ 1,234		$ (1,319)		$ 132	$ (178)	$ 164	$ (14)	$ 118	$ 1,234	$ (1,319)
Net income (loss) available to common stockholders - basic, as revised	245		1,202	[1]	(1,319)									129	(178)	159	(14)	115	1,202	(1,319)
Net income (loss) available to common stockholders - diluted, as revised	$ 245		$ 1,202	[1]	$ (1,319)									$ 101	$ (178)	$ 159	$ (14)	$ 110	$ 1,202	$ (1,319)
Denominator: [Abstract]
Basic weighted average shares	189,071,011	[2]	188,834,626	[1],[2]	192,505,045	[1],[2]	192,711,608	193,104,610	194,523,933	193,810,351	193,440,078	193,842,435	197,019,968	188,931,800	189,163,527	189,111,170	189,135,587	189,094,678	188,834,626	192,505,045
Diluted weighted average shares	190,312,913		189,897,021	[1]	192,505,045	[1]	196,746,771	193,104,610	195,631,960	193,810,351	197,762,488	194,904,830	197,019,968	192,581,064	189,163,527	190,219,197	189,135,587	193,031,189	189,897,021	192,505,045
Earnings Per Share [Abstract]
Net income (loss) per basic common share	$ 1.30		$ 6.36		$ (6.85)	[1]	$ 0.68	$ (0.92)	$ 0.84	$ (0.07)	$ 0.61	$ 6.36	$ (6.69)	$ 0.68	$ (0.94)	$ 0.84	$ (0.07)	$ 0.61	$ 6.36	$ (6.85)
Net income (loss) per diluted common share	$ 1.29		$ 6.33		$ (6.85)	[1]	$ 0.67	$ (0.92)	$ 0.84	$ (0.07)	$ 0.60	$ 6.33	$ (6.69)	$ 0.52	$ (0.94)	$ 0.84	$ (0.07)	$ 0.57	$ 6.33	$ (6.85)

[1] Amounts shown are revised.

[2] Includes 629,896, 506,714 and 565,819 of participating securities that met the service condition and were eligible to receive nonforfeitable dividends or dividend equivalents for the years ended December 31, 2013, 2012 and 2011, respectively.