Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net income	$ 734	$ 620	$ 1,395	$ 1,122
Preferred stock dividends	(36)	(36)	(91)	(91)
Dividends and undistributed earnings allocated to participating securities			(1)	(1)
Net income available to common shareholders	$ 698	$ 584	$ 1,303	$ 1,030
Basic average common shares	365,619	375,395	366,524	378,293
Effect of dilutive securities: common stock options and common stock awards (in shares)	4,791	5,520	4,891	5,196
Diluted average common shares	370,410	380,915	371,415	383,489
Anti-dilutive securities (in shares)	1,206	293	2	527
Earnings per Common Share:
Basic (in USD per share)	$ 1.91	$ 1.56	$ 3.55	$ 2.72
Diluted (in USD per share)	$ 1.88	$ 1.53	$ 3.51	$ 2.69