Earnings Per Common Share (EPS) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2022		Jun. 30, 2021		Jun. 30, 2022		Jun. 30, 2021
Basic and diluted:
Net income	$ 1,964		$ 2,280		$ 4,063		$ 4,515
Preferred dividends	(15)		(15)		(29)		(29)
Net income available to common shareholders	1,949		2,265		4,034		4,486
Earnings allocated to participating share awards	(15)		(16)		(31)		(31)
Net income attributable to common shareholders	$ 1,934		$ 2,249		$ 4,003		$ 4,455
Denominator:
Basic: Weighted-average common stock (in shares)	752,000		801,000		755,000		802,000
Add: Weighted-average stock options (in shares)	1,000		1,000		1,000		1,000
Diluted (in shares)	753,000		802,000		756,000		803,000
Basic EPS (in dollars per share)	$ 2.57	[1]	$ 2.81	[1]	$ 5.30	[2]	$ 5.55	[2]
Diluted EPS (in dollars per share)	$ 2.57	[1]	$ 2.80	[1]	$ 5.30	[2]	$ 5.54	[2]
Stock options
Denominator:
The dilutive effect of securities excluded from the calculation of earnings per share (in shares)	250		10		210		210

[1] Represents net income less (i) earnings allocated to participating share awards of $15 million and $16 million for the three months ended June 30, 2022 and 2021, respectively, and (ii) dividends on preferred shares of $15 million for both the three months ended June 30, 2022 and 2021.

[2] Represents net income less (i) earnings allocated to participating share awards of $31 million for both the six months ended June 30, 2022 and 2021, and (ii) dividends on preferred shares of $29 million for both the six months ended June 30, 2022 and 2021.