Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net income	$ 765	$ 685	$ 2,160	$ 1,807
Preferred stock dividends	(55)	(55)	(146)	(146)
Dividends and undistributed earnings allocated to participating securities	(1)	(1)	(2)	(2)
Net income available to common shareholders	$ 709	$ 629	$ 2,012	$ 1,659
Basic average common shares	374,963	372,765	369,368	376,430
Effect of dilutive securities: common stock options and common stock awards (in shares)	4,420	5,753	4,696	5,349
Diluted average common shares	379,383	378,518	374,064	381,779
Anti-dilutive securities (in shares)	1,360	0	871	250
Earnings per Common Share:
Basic (in USD per share)	$ 1.89	$ 1.69	$ 5.45	$ 4.41
Diluted (in USD per share)	$ 1.87	$ 1.66	$ 5.38	$ 4.35