Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Net income	$ 2,599	$ 2,177	$ 2,143
Preferred stock dividends	(188)	(182)	(173)
Dividends and undistributed earnings allocated to participating securities	(1)	(2)	(2)
Net income available to common shareholders	$ 2,410	$ 1,993	$ 1,968
Basic average common shares	371,983	374,793	391,485
Effect of dilutive securities: common stock options and common stock awards (in shares)	4,493	5,420	4,605
Diluted average common shares	376,476	380,213	396,090
Anti-dilutive securities (in shares)	1,011	188	2,143
Earnings per Common Share:
Basic (in USD per share)	$ 6.48	$ 5.32	$ 5.03
Diluted (in USD per share)	$ 6.40	$ 5.24	$ 4.97