Earnings Per Common Share (EPS) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021
Basic and diluted:
Net income		$ 2,099	$ 2,235
Preferred dividends		(14)	(14)
Net income available to common shareholders		2,085	2,221
Earnings allocated to participating share awards		(16)	(15)
Net income attributable to common shareholders		$ 2,069	$ 2,206
Denominator:
Basic: Weighted-average common stock (in shares)		757.0	804.0
Add: Weighted-average stock options (in shares)		1.0	1.0
Diluted (in shares)		758.0	805.0
Basic EPS (in dollars per share)	[1]	$ 2.73	$ 2.74
Diluted EPS (in dollars per share)	[1]	$ 2.73	$ 2.74
Stock options
Denominator:
The dilutive effect of securities excluded from the calculation of earnings per share (in shares)		0.1	0.3

[1] Represents net income less (i) earnings allocated to participating share awards of $16 million and $15 million for the three months ended March 31, 2022 and 2021, respectively, and (ii) dividends on preferred shares of $14 million for both the three months ended March 31, 2022 and 2021.