Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share Reconciliation [Abstract]
Net income	$ 733	$ 600
Participating share-based awards — allocated income	(5)	(5)
Net income available to common shareholders -- basic	728	595
Net income available to common shareholders -- diluted	$ 728	$ 595
Weighted average shares outstanding, basic (in shares)	252.1	254.4
Weighted average effects of dilutive securities - stock options and performance shares (in shares)	2.0	1.5
Weighted average shares outstanding, diluted (in shares)	254.1	255.9
Net income per common share, basic (in dollars per share)	$ 2.89	$ 2.34
Net income per common share, diluted (in dollars per share)	$ 2.87	$ 2.33