Reconciliation of Net Income/(Loss) to Net Income/(Loss) Available to Common Shareholders (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Income (Loss) Attributable to Parent	$ 1,933	$ 1,774	$ 1,344
Dividends, Preferred Stock, Cash	(64)	(42)	(37)
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic	(6)	(10)	(10)
Net Income (Loss) Available to Common Stockholders, Basic	$ 1,863	$ 1,722	$ 1,297
Average basic common shares	514,844	527,500	534,283
Stock options	2,000	1,000	1,000
Restricted stock	4,000	4,000	4,000
Weighted Average Number of Shares Outstanding, Diluted	520,586	533,391	539,093
Net income/(loss) per average common share - diluted	$ 3.58	$ 3.23	$ 2.41
Earnings Per Share, Basic	$ 3.62	$ 3.26	$ 2.43