CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Millions	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock, at Cost	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2017			491,000,000
Beginning balance at Dec. 31, 2017	$ 20,270	$ 247	$ 6	$ 18,781	$ 4,164	$ (2,108)	$ (820)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(215)				(215)
Dividends to preferred stockholders	(7)				(7)
Preferred stock issued (in shares)		1,000,000
Preferred stock issued	296	$ 296
Treasury stock purchased (in shares)			(8,000,000)
Treasury stock purchased	(325)					(325)
Share-based compensation plans (in shares)			1,000,000
Share-based compensation plans	18			18		0
Employee stock purchase plan shares purchased	7			7
Total comprehensive income:
Net income	813				813
Other comprehensive income	(390)						(390)
Total comprehensive income	423				813		(390)
Ending balance (in shares) at Jun. 30, 2018		1,000,000	484,000,000
Ending balance at Jun. 30, 2018	20,467	$ 543	$ 6	18,806	4,755	(2,433)	(1,210)
Beginning balance (in shares) at Mar. 31, 2018		0	488,000,000
Beginning balance at Mar. 31, 2018	20,059	$ 247	$ 6	18,797	4,437	(2,283)	(1,145)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(107)				(107)
Preferred stock issued (in shares)		1,000,000
Preferred stock issued	296	$ 296
Treasury stock purchased (in shares)			(4,000,000)
Treasury stock purchased	(150)					(150)
Share-based compensation plans (in shares)			0
Share-based compensation plans	5			5		0
Employee stock purchase plan shares purchased	4			4
Total comprehensive income:
Net income	425				425
Other comprehensive income	(65)						(65)
Total comprehensive income	360				425		(65)
Ending balance (in shares) at Jun. 30, 2018		1,000,000	484,000,000
Ending balance at Jun. 30, 2018	20,467	$ 543	$ 6	18,806	4,755	(2,433)	(1,210)
Beginning balance (in shares) at Dec. 31, 2018		1,000,000	466,000,000
Beginning balance at Dec. 31, 2018	20,817	$ 840	$ 6	18,815	5,385	(3,133)	(1,096)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(297)				(297)
Dividends to preferred stockholders	(33)				(33)
Preferred stock issued (in shares)		0
Preferred stock issued	$ 293	$ 293
Treasury stock purchased (in shares)	(9,287,644)		(9,000,000)
Treasury stock purchased	$ (320)					(320)
Share-based compensation plans (in shares)			1,000,000
Share-based compensation plans	37			37
Employee stock purchase plan shares purchased	8			8
Total comprehensive income:
Net income	892				892
Other comprehensive income	603						603
Total comprehensive income	1,495				892		603
Ending balance (in shares) at Jun. 30, 2019		1,000,000	458,000,000
Ending balance at Jun. 30, 2019	22,017	$ 1,133	$ 6	18,860	5,959	(3,453)	(488)
Beginning balance (in shares) at Mar. 31, 2019		1,000,000	461,000,000
Beginning balance at Mar. 31, 2019	21,531	$ 1,132	$ 6	18,847	5,672	(3,333)	(793)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(148)				(148)
Dividends to preferred stockholders	(18)				(18)
Preferred stock issued (in shares)		0
Preferred stock issued	1	$ 1
Treasury stock purchased (in shares)			(3,000,000)
Treasury stock purchased	(120)					(120)
Share-based compensation plans (in shares)			0
Share-based compensation plans	9			9		0
Employee stock purchase plan shares purchased	4			4
Total comprehensive income:
Net income	453				453
Other comprehensive income	305						305
Total comprehensive income	758				453		305
Ending balance (in shares) at Jun. 30, 2019		1,000,000	458,000,000
Ending balance at Jun. 30, 2019	$ 22,017	$ 1,133	$ 6	$ 18,860	$ 5,959	$ (3,453)	$ (488)