Earnings Per Common Share - Computation of Basic and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Income from continuing operations, net of tax	$ 12,394	$ 2,717	$ 5,533
Income (loss) from discontinued operations, net of tax	(4)	(3)	13
Net income	12,390	2,714	5,546
Dividends and undistributed earnings allocated to participating securities	(105)	(20)	(41)
Preferred stock dividends	(274)	(280)	(282)
Issuance cost for redeemed preferred stock	(46)	(39)	(31)
Net income available to common stockholders	$ 11,965	$ 2,375	$ 5,192
Total weighted-average basic common shares outstanding	442.5	457.8	467.6
Effect of dilutive securities:
Stock options	0.7	0.6	1.3
Other contingently issuable shares	1.0	0.5	1.0
Total effect of dilutive securities	1.7	1.1	2.3
Weighted Average Number of Shares Outstanding, Diluted, Total	444.2	458.9	469.9
Basic earnings per common share:
Net income from continuing operations	$ 27.05	$ 5.20	$ 11.07
Income (loss) from discontinued operations	(0.01)	(0.01)	0.03
Net income per basic common share	27.04	5.19	11.10
Diluted earnings per common share:
Net income from continuing operations	26.95	5.19	11.02
Income (loss) from discontinued operations	(0.01)	(0.01)	0.03
Net income per diluted common share	$ 26.94	$ 5.18	$ 11.05