Consolidated Statements of Changes in Equity - USD ($) $ in Millions		Total	Series D Preferred Stock [Member]	Series E Preferred Stock [Member]	Series F Preferred Stock [Member]	Preferred Stock [Member]	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Retained Earnings [Member] Series D Preferred Stock [Member]	Retained Earnings [Member] Series E Preferred Stock [Member]	Retained Earnings [Member] Series F Preferred Stock [Member]	Treasury Stock, at Cost [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interests [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance						$ 1,025	$ 1,257	$ 6,335	$ 10,335				$ (3,150)	$ (779)	$ 2
Cumulative effect from changes in accounting principle	[1]								(2)
Beginning Balance, Preferred Shares (in shares) at Dec. 31, 2017						521,000
Beginning Balance, Common Shares (in shares) at Dec. 31, 2017							1,069,084,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance						$ 1,025	$ 1,257	6,289	10,624				(3,260)	(991)	2
Net income (loss)		$ 418							418						0
Other comprehensive income (loss)		(212)												(212)
Deferred compensation								6
Cash dividends declared on common shares									(112)
Cash dividends declared on preferred stock										$ (7)	$ (8)
Open market common share repurchases (in shares)							(7,333,000)
Open market Common Share repurchases													(156)
Employee equity compensation program Common Share repurchases (in shares)							(2,066,000)
Employee equity compensation program Common Share repurchases													(43)
Common shares reissued (returned) for stock options and other employee benefit plans, shares							5,254,000
Common Shares reissued (returned) for stock options and other employee benefit plans								(52)					89
Ending Balance, Preferred Shares (in shares) at Mar. 31, 2018						521,000
Ending Balance, Common Shares (in shares) at Mar. 31, 2018							1,064,939,000
Ending Balance at Mar. 31, 2018						$ 1,025	$ 1,257	6,289	10,624				(3,260)	(991)	2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance						1,025	1,257	6,289	10,624				(3,260)	(991)	2
Beginning Balance		15,596				$ 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		15,926				$ 1,450	$ 1,257	6,259	11,771				(4,283)	(530)	2
Net income (loss)		407							407						0
Other comprehensive income (loss)		288												288
Deferred compensation								(3)
Cash dividends declared on common shares									(172)
Cash dividends declared on preferred stock										$ (6)	$ (8)	$ (6)
Open market common share repurchases (in shares)							(9,968,000)
Open market Common Share repurchases													(167)
Employee equity compensation program Common Share repurchases (in shares)							(1,823,000)
Employee equity compensation program Common Share repurchases								(2)					(32)
Common shares reissued (returned) for stock options and other employee benefit plans, shares							5,474,000
Common Shares reissued (returned) for stock options and other employee benefit plans								(67)					97
Net contribution from (distribution to) noncontrolling interests															1
Ending Balance, Preferred Shares (in shares) at Mar. 31, 2019			21,000	500,000	425,000	946,000
Ending Balance, Common Shares (in shares) at Mar. 31, 2019							1,013,186,000
Ending Balance at Mar. 31, 2019		15,926				$ 1,450	$ 1,257	6,259	11,771				(4,283)	(530)	2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		$ 15,926				$ 1,450	$ 1,257	$ 6,259	$ 11,771				$ (4,283)	$ (530)	$ 2

[1] Includes the impact of implementing ASU 2014-09, ASU 2016-01, and ASU 2017-12.