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	4,515					4,515
Other comprehensive loss	14				14	0
Repurchase of common shares	(1,346)		(2)	(134)		(1,210)
Other changes, primarily employee plans	94		1	111		(18)
Cash dividends declared preferred							$ (14)	$ (14)	$ (15)	$ (15)
Cash dividends declared common	(693)					(693)
Ending Balance at Jun. 30, 2021	25,539	0	160	11,858	(2,881)	16,402
Beginning Balance at Mar. 31, 2021	24,449	0	161	11,878	(2,898)	15,308
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,280					2,280
Other comprehensive loss	17				17	0
Repurchase of common shares	(908)		(1)	(85)		(822)
Other changes, primarily employee plans	62			65		(3)
Cash dividends declared preferred							$ (7)	$ (7)	$ (8)	$ (8)
Cash dividends declared common	(346)					(346)
Ending Balance at Jun. 30, 2021	25,539	0	160	11,858	(2,881)	16,402
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	4,063					4,063
Other comprehensive loss	(198)				(198)	0
Repurchase of common shares	(2,094)		(2)	(179)		(1,913)
Other changes, primarily employee plans	103			160		(57)
Cash dividends declared preferred											$ (29)	$ (29)
Cash dividends declared common	(787)					(787)
Ending Balance at Jun. 30, 2022	23,235	0	151	11,476	(3,143)	14,751
Beginning Balance at Mar. 31, 2022	22,383	0	151	11,451	(2,973)	13,754
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,964					1,964
Other comprehensive loss	(170)				(170)	0
Repurchase of common shares	(611)			(53)		(558)
Other changes, primarily employee plans	77			78		(1)
Cash dividends declared preferred											$ (15)	$ (15)
Cash dividends declared common	(393)					(393)
Ending Balance at Jun. 30, 2022	$ 23,235	$ 0	$ 151	$ 11,476	$ (3,143)	$ 14,751