Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net income	$ 508	$ 659
Preferred stock dividends	(55)	(55)
Dividends and undistributed earnings allocated to participating securities	(1)	(1)
Net income available to common shareholders	$ 452	$ 603
Basic average common shares	377,915	367,439
Effect of dilutive securities: common stock options and common stock awards (in shares)	3,788	5,180
Diluted average common shares	381,703	372,619
Anti-dilutive securities (in shares)	1,951	0
Earnings per common share:
Basic (in USD per share)	$ 1.20	$ 1.64
Diluted (in USD per share)	$ 1.18	$ 1.62