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	Cumulative Effect, Period of Adoption, Adjustment	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					$ 0	$ 1,900	$ 1,257	$ 6,281	$ 12,751					$ (4,946)	$ 738
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13 [Member]
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					$ 0	$ 1,900	$ 1,257	6,281	12,751					(4,946)	738
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	1,351									1,351
Other comprehensive income (loss)	(588)															(588)
Deferred compensation	0
Cash dividends declared on common shares	(360)									(360)
Cash dividends declared on preferred stock		$ (13)	$ (15)	$ (12)	$ (13)						$ (13)	$ (15)	$ (12)	$ (13)
Open market Common Share repurchases (in shares)								(20,979,000)
Open market Common Share repurchases	(435)														(435)
Employee equity compensation program Common Share repurchases (in shares)								(1,602,000)
Employee equity compensation program Common Share repurchases	(32)														(32)
Common shares reissued (returned) for stock options and other employee benefit plans (in shares)								7,084,000
Common shares reissued (returned) for stock options and other employee benefit plans	77								(49)						126
Ending Balance, Preferred Shares (in shares) at Jun. 30, 2021							1,396,000
Ending Balance, Common Shares (in shares) at Jun. 30, 2021								960,276,000
Ending balance at Jun. 30, 2021	17,941						$ 1,900	$ 1,257	6,232	13,689					(5,287)	150
Beginning Balance, Preferred Shares (in shares) at Mar. 31, 2021							1,396,000
Beginning Balance, Common Shares (in shares) at Mar. 31, 2021								972,587,000
Beginning balance at Mar. 31, 2021	17,634						$ 1,900	$ 1,257	6,213	13,166					(5,005)	103
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	729									729
Other comprehensive income (loss)	47															47
Deferred compensation	3								3
Cash dividends declared on common shares	(179)									(179)
Cash dividends declared on preferred stock		(6)	(8)	(6)	(7)						(6)	(8)	(6)	(7)
Open market Common Share repurchases (in shares)								(13,278,000)
Open market Common Share repurchases	(299)														(299)
Employee equity compensation program Common Share repurchases (in shares)								(26,000)
Employee equity compensation program Common Share repurchases	(1)														(1)
Common shares reissued (returned) for stock options and other employee benefit plans (in shares)								993,000
Common shares reissued (returned) for stock options and other employee benefit plans	34								16						18
Ending Balance, Preferred Shares (in shares) at Jun. 30, 2021							1,396,000
Ending Balance, Common Shares (in shares) at Jun. 30, 2021								960,276,000
Ending balance at Jun. 30, 2021	17,941						$ 1,900	$ 1,257	6,232	13,689					(5,287)	150
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)	981									981
Other comprehensive income (loss)	(3,580)															(3,580)
Deferred compensation	(6)								(6)
Cash dividends declared on common shares	(364)									(364)
Cash dividends declared on preferred stock		$ (12)	$ (16)	$ (12)	$ (12)						(12)	(16)	(12)	(12)
Open market Common Share repurchases	0
Employee equity compensation program Common Share repurchases (in shares)								(1,731,000)
Employee equity compensation program Common Share repurchases	(44)														(44)
Common shares reissued (returned) for stock options and other employee benefit plans (in shares)								5,524,000
Common shares reissued (returned) for stock options and other employee benefit plans	69								(31)						100
Ending Balance, Preferred Shares (in shares) at Jun. 30, 2022		21,000	500,000	425,000	450,000		1,396,000
Ending Balance, Common Shares (in shares) at Jun. 30, 2022								932,643,000
Ending balance at Jun. 30, 2022	14,427						$ 1,900	$ 1,257	6,241	15,118					(5,923)	(4,166)
Beginning Balance, Preferred Shares (in shares) at Mar. 31, 2022							1,396,000
Beginning Balance, Common Shares (in shares) at Mar. 31, 2022								932,398,000
Beginning balance at Mar. 31, 2022	15,308						$ 1,900	$ 1,257	6,214	14,793					(5,927)	(2,929)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	533									533
Other comprehensive income (loss)	(1,237)															(1,237)
Deferred compensation	0
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	0
Employee equity compensation program Common Share repurchases (in shares)								(24,000)
Employee equity compensation program Common Share repurchases	0
Common shares reissued (returned) for stock options and other employee benefit plans (in shares)								269,000
Common shares reissued (returned) for stock options and other employee benefit plans	31								27						4
Ending Balance, Preferred Shares (in shares) at Jun. 30, 2022		21,000	500,000	425,000	450,000		1,396,000
Ending Balance, Common Shares (in shares) at Jun. 30, 2022								932,643,000
Ending balance at Jun. 30, 2022	$ 14,427						$ 1,900	$ 1,257	$ 6,241	$ 15,118					$ (5,923)	$ (4,166)