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 B Preferred Stock	Series B Preferred Stock Retained Earnings	Series C Preferred Stock	Series C Preferred Stock Retained Earnings	Series D Preferred Stock	Series D 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	6,341					6,341
Other comprehensive loss	(68)				(68)	0
Preferred shares issued	1,584			1,584		0
Redemption of preferred shares	(850)			(841)		(9)
Repurchase of common shares	(4,646)		(6)	(400)		(4,240)
Other changes, primarily employee plans	160		1	177		(18)
Cash dividends declared preferred							$ (21)	$ (21)	$ (22)	$ (22)	$ (6)	$ (6)
Cash dividends declared common	(1,030)					(1,030)
Ending Balance at Sep. 30, 2021	24,426	0	156	12,401	(2,963)	14,832
Beginning Balance at Jun. 30, 2021	25,539	0	160	11,858	(2,881)	16,402
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,826					1,826
Other comprehensive loss	(82)				(82)	0
Preferred shares issued	1,584			1,584		0
Redemption of preferred shares	(850)			(841)		(9)
Repurchase of common shares	(3,300)		(4)	(266)		(3,030)
Other changes, primarily employee plans	66			66		0
Cash dividends declared preferred							$ (7)	$ (7)	$ (7)	$ (7)	(6)	(6)
Cash dividends declared common	(337)					(337)
Ending Balance at Sep. 30, 2021	24,426	0	156	12,401	(2,963)	14,832
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	5,942					5,942
Other comprehensive loss	(432)				(432)	0
Repurchase of common shares	(2,694)		(3)	(240)		(2,451)
Other changes, primarily employee plans	168			227		(59)
Cash dividends declared preferred											(43)	(43)
Cash dividends declared common	(1,178)					(1,178)
Ending Balance at Sep. 30, 2022	23,940	0	150	11,482	(3,377)	15,685
Beginning Balance at Jun. 30, 2022	23,235	0	151	11,476	(3,143)	14,751
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,879					1,879
Other comprehensive loss	(234)				(234)	0
Repurchase of common shares	(600)		(1)	(61)		(538)
Other changes, primarily employee plans	65			67		(2)
Cash dividends declared preferred											$ (14)	$ (14)
Cash dividends declared common	(391)					(391)
Ending Balance at Sep. 30, 2022	$ 23,940	$ 0	$ 150	$ 11,482	$ (3,377)	$ 15,685