Consolidated Statements of Changes in Equity - USD ($) $ in Millions	Total	Series D Preferred Stock	Series E Preferred Stock	Series F Preferred Stock	Series G Preferred Stock	Preferred Stock	Common Stock	Capital Surplus	Retained Earnings	Retained Earnings Series D Preferred Stock	Retained Earnings Series E Preferred Stock	Retained Earnings Series F Preferred Stock	Retained Earnings Series G Preferred Stock	Treasury Stock, at Cost	Accumulated Other Comprehensive Income (Loss)
Beginning Balance, Preferred Shares (in shares) at Dec. 31, 2020						1,396,000
Beginning Balance, Common Shares (in shares) at Dec. 31, 2020							975,773,000
Beginning balance at Dec. 31, 2020	$ 17,981					$ 1,900	$ 1,257	$ 6,281	$ 12,751					$ (4,946)	$ 738
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	622								622
Other comprehensive income (loss)	(635)														(635)
Deferred compensation	(3)							(3)
Cash dividends declared on common shares	(180)								(180)
Cash dividends declared on preferred stock		$ (7)	$ (8)	$ (6)	$ (6)					$ (7)	$ (8)	$ (6)	$ (6)
Open market Common Share repurchases (in shares)						(7,701,000)
Open market Common Share repurchases	(135)													(135)
Employee equity compensation program Common Share repurchases (in shares)							(1,576,000)
Employee equity compensation program Common Share repurchases	(31)													(31)
Common shares reissued (returned) for stock options and other employee benefit plans (in shares)							6,091,000
Common shares reissued (returned) for stock options and other employee benefit plans	42							(65)						107
Other	0								0
Ending Balance, Preferred Shares (in shares) at Mar. 31, 2021						1,396,000
Ending Balance, Common Shares (in shares) at Mar. 31, 2021							972,587,000
Ending balance at Mar. 31, 2021	17,634					$ 1,900	$ 1,257	6,213	13,166					(5,005)	103
Beginning Balance, Preferred Shares (in shares) at Dec. 31, 2021						1,396,000
Beginning Balance, Common Shares (in shares) at Dec. 31, 2021							928,850,000
Beginning balance at Dec. 31, 2021	17,423					$ 1,900	$ 1,257	6,278	14,553					(5,979)	(586)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	448								448
Other comprehensive income (loss)	(2,343)														(2,343)
Deferred compensation	(7)							(7)
Cash dividends declared on common shares	(182)								(182)
Cash dividends declared on preferred stock		$ (6)	$ (8)	$ (6)	$ (6)					$ (6)	$ (8)	$ (6)	$ (6)
Open market Common Share repurchases (in shares)							0
Open market Common Share repurchases	0													0
Employee equity compensation program Common Share repurchases (in shares)							(1,707,000)
Employee equity compensation program Common Share repurchases	(44)													(44)
Common shares reissued (returned) for stock options and other employee benefit plans (in shares)							5,255,000
Common shares reissued (returned) for stock options and other employee benefit plans	39							(57)						96
Ending Balance, Preferred Shares (in shares) at Mar. 31, 2022		21,000	500,000	425,000	450,000	1,396,000
Ending Balance, Common Shares (in shares) at Mar. 31, 2022							932,398,000
Ending balance at Mar. 31, 2022	$ 15,308					$ 1,900	$ 1,257	$ 6,214	$ 14,793					$ (5,927)	$ (2,929)