Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Preferred Shares	Common Shares	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Series D Preferred Stock	Series D Preferred Stock Retained Earnings	Series B Preferred Stock	Series B Preferred Stock Retained Earnings	Series C Preferred Stock	Series C Preferred Stock Retained Earnings
Beginning Balance at Dec. 31, 2020	$ 22,984	$ 0	$ 161	$ 11,881	$ (2,895)	$ 13,837
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,235					2,235
Other comprehensive loss	(3)				(3)	0
Repurchase of common shares	(438)		(1)	(49)		(388)
Other changes, primarily employee plans	32		1	46		(15)
Cash dividends declared preferred									$ (7)	$ (7)	$ (7)	$ (7)
Cash dividends declared common	(347)					(347)
Ending Balance at Mar. 31, 2021	24,449	0	161	11,878	(2,898)	15,308
Beginning Balance at Dec. 31, 2021	22,177	0	153	11,495	(2,945)	13,474
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,099					2,099
Other comprehensive loss	(28)				(28)
Repurchase of common shares	(1,483)		(2)	(126)		(1,355)
Other changes, primarily employee plans	26			82		(56)
Cash dividends declared preferred							$ (14)	$ (14)
Cash dividends declared common	(394)					(394)
Ending Balance at Mar. 31, 2022	$ 22,383	$ 0	$ 151	$ 11,451	$ (2,973)	$ 13,754