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)	Noncontrolling Interests	Cumulative Effect, Period of Adoption, Adjustment Retained Earnings	[1]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance						$ 1,450	$ 1,257	$ 6,331	$ 11,556					$ (4,181)	$ (818)	$ 1
Beginning Balance, Preferred Shares (in shares) at Dec. 31, 2018						946,000
Beginning Balance, Common Shares (in shares) at Dec. 31, 2018							1,019,503,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance						$ 1,900	$ 1,257	6,287	12,209					(4,696)	159	0
Net income (loss)	$ 1,248								1,248
Other comprehensive income (loss)	977														977
Deferred compensation								6
Cash dividends declared on common shares									(525)
Cash dividends declared on preferred stock										$ (20)	$ (23)	$ (18)	$ (9)
Issuance of Series G Preferred Stock (in shares)						450,000
Issuance of Series G Preferred Stock						$ 450		(15)
Open market common share repurchases (in shares)							(35,400,000)
Open market Common Share repurchases														(594)
Employee equity compensation program Common Share repurchases (in shares)							(1,880,000)
Employee equity compensation program Common Share repurchases								(3)						(33)
Common shares reissued (returned) for stock options and other employee benefit plans, shares							6,315,000
Common Shares reissued (returned) for stock options and other employee benefit plans								(32)						112
Net contribution from (distribution to) noncontrolling interests																(1)
Ending Balance, Preferred Shares (in shares) at Sep. 30, 2019						1,396,000
Ending Balance, Common Shares (in shares) at Sep. 30, 2019							988,538,000
Ending Balance at Sep. 30, 2019						$ 1,900	$ 1,257	6,287	12,209					(4,696)	159	0
Beginning Balance, Preferred Shares (in shares) at Dec. 31, 2018						946,000
Beginning Balance, Common Shares (in shares) at Dec. 31, 2018							1,019,503,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 17,038					$ 1,900	$ 1,257	6,295	12,469					(4,909)	26	0	$ (230)
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Ending Balance, Preferred Shares (in shares) at Dec. 31, 2019						1,396,000
Ending Balance, Common Shares (in shares) at Dec. 31, 2019							977,189,000
Ending Balance at Dec. 31, 2019	$ 17,038					$ 1,900	$ 1,257	6,295	12,469					(4,909)	26	0	(230)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance						$ 1,900	$ 1,257	6,266	12,005					(4,457)	(2)	2
Beginning Balance, Preferred Shares (in shares) at Jun. 30, 2019						1,396,000
Beginning Balance, Common Shares (in shares) at Jun. 30, 2019							1,003,114,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance						$ 1,900	$ 1,257	6,287	12,209					(4,696)	159	0
Net income (loss)	416								416
Other comprehensive income (loss)	161
Deferred compensation								5
Cash dividends declared on common shares									(182)						161
Cash dividends declared on preferred stock										(7)	(8)	(6)	(9)
Issuance of Series G Preferred Stock (in shares)						0
Issuance of Series G Preferred Stock						$ 0		0
Open market common share repurchases (in shares)							(15,075,000)
Open market Common Share repurchases														(248)
Employee equity compensation program Common Share repurchases (in shares)							(2,000)
Employee equity compensation program Common Share repurchases								0						0
Common shares reissued (returned) for stock options and other employee benefit plans, shares							501,000
Common Shares reissued (returned) for stock options and other employee benefit plans								16						9
Net contribution from (distribution to) noncontrolling interests																(2)
Ending Balance, Preferred Shares (in shares) at Sep. 30, 2019						1,396,000
Ending Balance, Common Shares (in shares) at Sep. 30, 2019							988,538,000
Ending Balance at Sep. 30, 2019						$ 1,900	$ 1,257	6,287	12,209					(4,696)	159	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance						1,900	1,257	6,287	12,209					(4,696)	159	0
Beginning Balance	17,038					$ 1,900	$ 1,257	6,295	12,469					(4,909)	26	0	$ (230)
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 17,722					$ 1,900	$ 1,257	6,263	12,375					(4,940)	867	0
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Net income (loss)	$ 761								761
Other comprehensive income (loss)	841														841
Deferred compensation								2
Cash dividends declared on common shares									(542)
Cash dividends declared on preferred stock										(20)	(23)	(18)	(19)
Open market common share repurchases (in shares)							(6,067,000)
Open market Common Share repurchases														(117)
Employee equity compensation program Common Share repurchases (in shares)							(1,815,000)
Employee equity compensation program Common Share repurchases								(34)						(36)
Common shares reissued (returned) for stock options and other employee benefit plans, shares							6,898,000
Common Shares reissued (returned) for stock options and other employee benefit plans														122
Other									(3)
Ending Balance, Preferred Shares (in shares) at Sep. 30, 2020		21,000	500,000	425,000	450,000	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	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance						$ 1,900	$ 1,257	6,240	12,154					(4,945)	936	0
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	17,722					$ 1,900	$ 1,257	6,263	12,375					(4,940)	867	0
Net income (loss)	428								428
Other comprehensive income (loss)	(69)														(69)
Deferred compensation								2
Cash dividends declared on common shares									(180)
Cash dividends declared on preferred stock										$ (7)	$ (8)	$ (6)	$ (6)
Open market common share repurchases (in shares)							0
Open market Common Share repurchases														0
Employee equity compensation program Common Share repurchases (in shares)							(1,000)
Employee equity compensation program Common Share repurchases								21						0
Common shares reissued (returned) for stock options and other employee benefit plans, shares							259,000
Common Shares reissued (returned) for stock options and other employee benefit plans														5
Other									0
Ending Balance, Preferred Shares (in shares) at Sep. 30, 2020		21,000	500,000	425,000	450,000	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	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 17,722					$ 1,900	$ 1,257	$ 6,263	$ 12,375					$ (4,940)	$ 867	$ 0

[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 (“Basis of Presentation and Accounting Policies”) for more information on our adoption of this guidance and the impact to our results of operations.