Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Series B Preferred Stock	Series C Preferred Stock	Series D Preferred Stock	Preferred Shares	Common Shares	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings Series B Preferred Stock	Retained Earnings Series C Preferred Stock	Retained Earnings Series D Preferred Stock
Beginning Balance at Dec. 31, 2018	$ 22,290					$ 0	$ 170	$ 12,218	$ (2,597)	$ 12,499
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	6,759									6,759
Other comprehensive (loss) income	(140)								(140)
Repurchase of common shares	(4,585)						(8)	(671)		(3,906)
Other changes, primarily employee plans	186						1	227		(42)
Cash dividends declared preferred			$ (39)	$ (42)								$ (39)	$ (42)
Cash dividends declared common	(1,358)									(1,358)
Ending Balance at Dec. 31, 2019	$ 23,071	$ (882)				0	163	11,774	(2,737)	13,871	$ (882)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13 [Member]
Net income	$ 3,135									3,135
Other comprehensive (loss) income	(158)								(158)
Repurchase of common shares	(875)						(2)	(105)		(768)
Other changes, primarily employee plans	164							212		(48)
Cash dividends declared preferred			(34)	(45)								(34)	(45)
Cash dividends declared common	(1,392)									(1,392)
Ending Balance at Dec. 31, 2020	22,984					0	161	11,881	(2,895)	13,837
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	8,060									8,060
Other comprehensive (loss) income	(50)								(50)
Preferred shares issued	1,584							1,584
Redemption of preferred shares	(1,600)							(1,584)		(16)
Repurchase of common shares	(7,598)						(9)	(631)		(6,958)
Other changes, primarily employee plans	227						1	245		(19)
Cash dividends declared preferred			$ (27)	$ (23)	$ (21)							$ (27)	$ (23)	$ (21)
Cash dividends declared common	(1,359)									(1,359)
Ending Balance at Dec. 31, 2021	$ 22,177					$ 0	$ 153	$ 11,495	$ (2,945)	$ 13,474