Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Income (Numerator)
Net income	$ 599	$ 475
Net income applicable to common stock for computing basic earnings per common share	599	475
Net income as adjusted for purposes of computing diluted earnings per common share	$ 599	$ 475
Weighted-average number of shares:
Outstanding during period (in shares)	1,027,217	1,100,350
Non-vested restricted stock (in shares)	(18,787)	(17,876)
Weighted average shares outstanding for computing basic earnings per common share (in shares)	1,008,430	1,082,474
Incremental common shares attributable to dilutive securities:
Shares issuable under convertible securities (in shares)	10	10
Shares issuable under incentive compensation plans (in shares)	6,775	9,102
Number of shares as adjusted for purposes of computing diluted earnings per common share (in shares)	1,015,215	1,091,586
Basic earnings per common share (in dollars per share)	$ 0.59	$ 0.44
Diluted earnings per common share (in dollars per share)	$ 0.59	$ 0.44
Number of shares of common stock excluded from the computation of diluted earnings per share (less than) (in shares)	8,200	1,000