Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net income	$ 563	$ 581	$ 1,550	$ 1,404
Preferred stock dividends	(55)	(42)	(137)	(102)
Dividends and undistributed earnings allocated to participating securities	(1)	0	(2)	(1)
Net income available to common shareholders	$ 507	$ 539	$ 1,411	$ 1,301
Basic average common shares	388,358	406,612	393,959	409,816
Effect of dilutive securities: common stock options and common stock awards (in shares)	4,854	5,555	4,454	5,956
Diluted average common shares	393,212	412,167	398,413	415,772
Anti-dilutive securities (in shares)	2,166	619	3,027	675
Earnings per Common Share:
Basic (in USD per share)	$ 1.31	$ 1.33	$ 3.58	$ 3.18
Diluted (in USD per share)	$ 1.29	$ 1.31	$ 3.54	$ 3.13