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
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	6,266	12,005					(4,457)	(2)	2
Net income (loss)	$ 832								832
Other comprehensive income (loss)	816														816
Deferred compensation								1
Cash dividends declared on common shares									(343)
Cash dividends declared on preferred stock										$ (13)	$ (15)	$ (12)
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)							(20,325,000)
Open market Common Share repurchases														(346)
Employee equity compensation program Common Share repurchases (in shares)							(1,878,000)
Employee equity compensation program Common Share repurchases								(3)						(33)
Common shares reissued (returned) for stock options and other employee benefit plans, shares							5,814,000
Common Shares reissued (returned) for stock options and other employee benefit plans								(48)						103
Net contribution from (distribution to) noncontrolling interests																1
Ending Balance, Preferred Shares (in shares) at Jun. 30, 2019						1,396,000
Ending Balance, Common Shares (in shares) at Jun. 30, 2019							1,003,114,000
Ending Balance at Jun. 30, 2019						$ 1,900	$ 1,257	6,266	12,005					(4,457)	(2)	2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance						$ 1,450	$ 1,257	6,259	11,771					(4,283)	(530)	2
Beginning Balance, Preferred Shares (in shares) at Mar. 31, 2019						946,000
Beginning Balance, Common Shares (in shares) at Mar. 31, 2019							1,013,186,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance						$ 1,900	$ 1,257	6,266	12,005					(4,457)	(2)	2
Net income (loss)	425								425
Other comprehensive income (loss)	528
Deferred compensation								4
Cash dividends declared on common shares									(171)						528
Cash dividends declared on preferred stock										(7)	(7)	(6)
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)							(10,357,000)
Open market Common Share repurchases														(179)
Employee equity compensation program Common Share repurchases (in shares)							(55,000)
Employee equity compensation program Common Share repurchases								(1)						(1)
Common shares reissued (returned) for stock options and other employee benefit plans, shares							340,000
Common Shares reissued (returned) for stock options and other employee benefit plans								19						6
Ending Balance, Preferred Shares (in shares) at Jun. 30, 2019						1,396,000
Ending Balance, Common Shares (in shares) at Jun. 30, 2019							1,003,114,000
Ending Balance at Jun. 30, 2019						$ 1,900	$ 1,257	6,266	12,005					(4,457)	(2)	2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance						1,900	1,257	6,266	12,005					(4,457)	(2)	2
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	17,542					$ 1,900	$ 1,257	6,240	12,154					(4,945)	936	0
Net income (loss)	333								333
Other comprehensive income (loss)	910														910
Cash dividends declared on common shares									(362)
Cash dividends declared on preferred stock										(13)	(15)	(12)	$ (13)
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)							(1,814,000)
Employee equity compensation program Common Share repurchases								(55)						(36)
Other									(3)
Common shares reissued (returned) for stock options and other employee benefit plans, shares							6,639,000
Common Shares reissued (returned) for stock options and other employee benefit plans														117
Ending Balance, Preferred Shares (in shares) at Jun. 30, 2020		21,000	500,000	425,000	450,000	1,396,000
Ending Balance, Common Shares (in shares) at Jun. 30, 2020							975,947,000
Ending Balance at Jun. 30, 2020	17,542					$ 1,900	$ 1,257	6,240	12,154					(4,945)	936	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance						$ 1,900	$ 1,257	6,222	12,174					(4,956)	814	0
Beginning Balance, Preferred Shares (in shares) at Mar. 31, 2020						1,396,000
Beginning Balance, Common Shares (in shares) at Mar. 31, 2020							975,319,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	17,542					$ 1,900	$ 1,257	6,240	12,154					(4,945)	936	0
Net income (loss)	187								187
Other comprehensive income (loss)	122														122
Deferred compensation								1
Cash dividends declared on common shares									(181)
Cash dividends declared on preferred stock										$ (6)	$ (7)	$ (6)	$ (7)
Employee equity compensation program Common Share repurchases (in shares)							(19,000)
Employee equity compensation program Common Share repurchases								17						(1)
Common shares reissued (returned) for stock options and other employee benefit plans, shares							647,000
Common Shares reissued (returned) for stock options and other employee benefit plans														12
Ending Balance, Preferred Shares (in shares) at Jun. 30, 2020		21,000	500,000	425,000	450,000	1,396,000
Ending Balance, Common Shares (in shares) at Jun. 30, 2020							975,947,000
Ending Balance at Jun. 30, 2020	17,542					$ 1,900	$ 1,257	6,240	12,154					(4,945)	936	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 17,542					$ 1,900	$ 1,257	$ 6,240	$ 12,154					$ (4,945)	$ 936	$ 0