Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income	$ 2,242	$ 2,593	$ 2,156
Preferred stock dividends	(232)	(188)	(182)
Dividends and undistributed earnings allocated to participating securities	(1)	(1)	(2)
Net income available to common shareholders	$ 2,009	$ 2,404	$ 1,972
Basic average common shares	369,911	371,983	374,793
Effect of dilutive securities: common stock options and common stock awards (in shares)	3,755	4,493	5,420
Diluted average common shares	373,666	376,476	380,213
Anti-dilutive securities (in shares)	2,052	1,011	188
Earnings per common share:
Basic (in USD per share)	$ 5.43	$ 6.46	$ 5.26
Diluted (in USD per share)	$ 5.38	$ 6.39	$ 5.19