Reconciliation of Net Income/(Loss) to Net Income/(Loss) Available to Common Shareholders (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Net income	$ 352		$ 250
Dividends, Preferred Stock, Cash	(9)	[1]	(3)
Undistributed Earnings Allocated to Participating Securities	(3)		(2)
Net income/(loss) available to common shareholders	340		245
Average basic common shares	535,680,000		533,100,000
Stock options	1,000,000		1,000,000
Restricted stock	3,000,000		2,000,000
Average diluted common shares	539,862,000		536,407,000
Net income/(loss) per average common share - diluted	$ 0.63		$ 0.46
Net income/(loss) per average common share - basic	$ 0.64		$ 0.46
Retained Earnings [Member]
Net income	352		250
Dividends, Preferred Stock, Cash	$ (9)	[1]	$ (3)

[1] Dividends were $1,000 per share for Perpetual Preferred Stock Series A and B and $1,387 per share for Perpetual Preferred Stock Series E for the three months ended March 31, 2013.