Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income	$ 2,143	$ 1,980	$ 2,022
Preferred stock dividends	(173)	(130)	(61)
Dividends and undistributed earnings allocated to participating securities	(2)	(2)	(3)
Net income available to common shareholders	$ 1,968	$ 1,848	$ 1,958
Basic average common shares	391,485	407,856	424,223
Effect of dilutive securities: common stock options and common stock awards (in shares)	4,605	5,782	7,784
Diluted average common shares	396,090	413,638	432,007
Anti-dilutive securities (in shares)	2,143	661	1,498
Earnings per Common Share:
Basic (in USD per share)	$ 5.03	$ 4.53	$ 4.62
Diluted (in USD per share)	$ 4.97	$ 4.47	$ 4.53