Earnings Per Common Share (EPS) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Basic and diluted:
Net income		$ 8,060	$ 3,135	$ 6,759
Preferred dividends		(71)	(79)	(81)
Equity-related adjustments		(16)	0	0
Net income available to common shareholders		7,973	3,056	6,678
Earnings allocated to participating share awards		(56)	(20)	(47)
Net income attributable to common shareholders		$ 7,917	$ 3,036	$ 6,631
Denominator:
Basic: Weighted-average common stock (in shares)		789,000	805,000	828,000
Add: Weighted-average stock options (in shares)		1,000	1,000	2,000
Diluted (in shares)		790,000	806,000	830,000
Basic EPS (in dollars per share)	[1]	$ 10.04	$ 3.77	$ 8.00
Diluted EPS (in dollars per share)	[1]	$ 10.02	$ 3.77	$ 7.99
Stock Option
Denominator:
Antidilutive securities excluded from computation of earnings per share (in shares)		10	530	200

[1] Represents net income less (i) earnings allocated to participating share awards of $56 million, $20 million and $47 million for the years ended December 31, 2021, 2020 and 2019, respectively, (ii) dividends on preferred shares of $71 million, $79 million and $81 million for the years ended December 31, 2021, 2020 and 2019, respectively, and (iii) equity-related adjustments of $16 million related to the redemption of preferred shares for the year ended December 31, 2021.