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)	Cumulative Effect, Period of Adoption, Adjustment	[1]	Cumulative Effect, Period of Adoption, Adjustment Retained Earnings	[1]
Beginning Balance, Preferred Shares (in shares) at Dec. 31, 2019						1,396,000
Beginning Balance, Common Shares (in shares) at Dec. 31, 2019							977,189,000
Beginning balance at Dec. 31, 2019	$ 17,038					$ 1,900	$ 1,257	$ 6,295	$ 12,469					$ (4,909)	$ 26	$ (230)		$ (230)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	761								761
Other comprehensive income (loss)	841														841
Deferred compensation	2							2
Cash dividends declared on common shares	(542)								(542)
Cash dividends declared on preferred stock		$ (20)	$ (23)	$ (18)	$ (19)					$ (20)	$ (23)	$ (18)	$ (19)
Open market Common Share repurchases (in shares)							(6,067,000)
Open market Common Share repurchases	(117)													(117)
Employee equity compensation program Common Share repurchases (in shares)							(1,815,000)
Employee equity compensation program Common Share repurchases	(70)							(34)						(36)
Common shares reissued (returned) for stock options and other employee benefit plans (in shares)							6,898,000
Common shares reissued (returned) for stock options and other employee benefit plans	122													122
Other	(3)								(3)
Ending Balance, Preferred Shares (in shares) at Sep. 30, 2020						1,396,000
Ending Balance, Common Shares (in shares) at Sep. 30, 2020							976,205,000
Ending balance at Sep. 30, 2020	17,722					$ 1,900	$ 1,257	6,263	12,375					(4,940)	867
Beginning Balance, Preferred Shares (in shares) at Jun. 30, 2020						1,396,000
Beginning Balance, Common Shares (in shares) at Jun. 30, 2020							975,947,000
Beginning balance at Jun. 30, 2020	17,542					$ 1,900	$ 1,257	6,240	12,154					(4,945)	936
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	428								428
Other comprehensive income (loss)	(69)														(69)
Deferred compensation	2							2
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)							0
Open market Common Share repurchases	0													0
Employee equity compensation program Common Share repurchases (in shares)							(1,000)
Employee equity compensation program Common Share repurchases	21							21						0
Common shares reissued (returned) for stock options and other employee benefit plans (in shares)							259,000
Common shares reissued (returned) for stock options and other employee benefit plans	5							0						5
Ending Balance, Preferred Shares (in shares) at Sep. 30, 2020						1,396,000
Ending Balance, Common Shares (in shares) at Sep. 30, 2020							976,205,000
Ending balance at Sep. 30, 2020	17,722					$ 1,900	$ 1,257	6,263	12,375					(4,940)	867
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)	1,996								1,996
Other comprehensive income (loss)	(783)														(783)
Deferred compensation	5							5
Cash dividends declared on common shares	(534)								(534)
Cash dividends declared on preferred stock		$ (20)	$ (23)	$ (18)	$ (19)					(20)	(23)	(18)	(19)
Open market Common Share repurchases (in shares)							(27,346,000)
Open market Common Share repurchases	(559)													(559)
Employee equity compensation program Common Share repurchases (in shares)							(1,604,000)
Employee equity compensation program Common Share repurchases	(32)													(32)
Common shares reissued (returned) for stock options and other employee benefit plans (in shares)							7,274,000
Common shares reissued (returned) for stock options and other employee benefit plans	101							(28)						129
Common share purchases under accelerated repurchase program (in shares)							(23,553,000)
Common share purchases under ASR program	(585)							(117)						(468)
Ending Balance, Preferred Shares (in shares) at Sep. 30, 2021		21,000	500,000	425,000	450,000	1,396,000
Ending Balance, Common Shares (in shares) at Sep. 30, 2021							930,544,000
Ending balance at Sep. 30, 2021	17,510					$ 1,900	$ 1,257	6,141	14,133					(5,876)	(45)
Beginning Balance, Preferred Shares (in shares) at Jun. 30, 2021						1,396,000
Beginning Balance, Common Shares (in shares) at Jun. 30, 2021							960,276,000
Beginning balance at Jun. 30, 2021	17,941					$ 1,900	$ 1,257	6,232	13,689					(5,287)	150
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	645								645
Other comprehensive income (loss)	(195)														(195)
Deferred compensation	5							5
Cash dividends declared on common shares	(176)								(176)
Cash dividends declared on preferred stock		$ (6)	$ (7)	$ (7)	$ (5)					$ (6)	$ (7)	$ (7)	$ (5)
Open market Common Share repurchases (in shares)							(6,367,000)
Open market Common Share repurchases	(125)													(125)
Employee equity compensation program Common Share repurchases (in shares)							(3,000)
Employee equity compensation program Common Share repurchases	0							0						0
Common shares reissued (returned) for stock options and other employee benefit plans (in shares)							191,000
Common shares reissued (returned) for stock options and other employee benefit plans	25							21						4
Common share purchases under accelerated repurchase program (in shares)							(23,553,000)
Common share purchases under ASR program	(585)							(117)						(468)
Ending Balance, Preferred Shares (in shares) at Sep. 30, 2021		21,000	500,000	425,000	450,000	1,396,000
Ending Balance, Common Shares (in shares) at Sep. 30, 2021							930,544,000
Ending balance at Sep. 30, 2021	$ 17,510					$ 1,900	$ 1,257	$ 6,141	$ 14,133					$ (5,876)	$ (45)

[1] Includes the impact of implementing ASU 2016-13, Financial Instruments - Credit Losses (ASC 326): Measurement of Credit Losses on Financial Instruments. See Note 1 (“Summary of Significant Accounting Policies) in our 2020 Form 10-K for more information on our adoption of this guidance and the impact to our results of operations.