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		0	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	(344)				(344)
Dividends to preferred stockholders	(14)				(14)
Preferred stock issued (in shares)		1,000,000
Preferred stock issued	296	$ 296
Treasury stock purchased (in shares)			(18,000,000)
Treasury stock purchased	(725)					(725)
Share-based compensation plans (in shares)			1,000,000
Share-based compensation plans	24			24		0
Employee stock purchase plan shares purchased	11			11
Total comprehensive income:
Net income	1,256				1,256
Other comprehensive income	(498)						(498)
Total comprehensive income	758				1,256		(498)
Ending balance (in shares) at Sep. 30, 2018		1,000,000	474,000,000
Ending balance at Sep. 30, 2018	20,276	$ 543	$ 6	18,816	5,062	(2,833)	(1,318)
Beginning balance (in shares) at Jun. 30, 2018		1,000,000	484,000,000
Beginning balance at Jun. 30, 2018	20,467	$ 543	$ 6	18,806	4,755	(2,433)	(1,210)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(129)				(129)
Dividends to preferred stockholders	(7)				(7)
Preferred stock issued (in shares)		0
Preferred stock issued		$ 0
Treasury stock purchased (in shares)			(10,000,000)
Treasury stock purchased	(400)					(400)
Share-based compensation plans (in shares)			0
Share-based compensation plans	6			6		0
Employee stock purchase plan shares purchased	4			4
Total comprehensive income:
Net income	443				443
Other comprehensive income	(108)						(108)
Total comprehensive income	335				443		(108)
Ending balance (in shares) at Sep. 30, 2018		1,000,000	474,000,000
Ending balance at Sep. 30, 2018	20,276	$ 543	$ 6	18,816	5,062	(2,833)	(1,318)
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	(459)				(459)
Dividends to preferred stockholders	(50)				(50)
Preferred stock issued (in shares)		0
Preferred stock issued	$ 293	$ 293
Treasury stock purchased (in shares)	(23,399,661)		(23,000,000)
Treasury stock purchased	$ (820)					(820)
Share-based compensation plans (in shares)			1,000,000
Share-based compensation plans	48			48
Employee stock purchase plan shares purchased	13			13
Total comprehensive income:
Net income	1,341				1,341
Other comprehensive income	651						651
Total comprehensive income	1,992				1,341		651
Ending balance (in shares) at Sep. 30, 2019		1,000,000	444,000,000
Ending balance at Sep. 30, 2019	21,851	$ 1,133	$ 6	18,876	6,229	(3,953)	(440)
Beginning balance (in shares) at Jun. 30, 2019		1,000,000	458,000,000
Beginning balance at Jun. 30, 2019	22,017	$ 1,133	$ 6	18,860	5,959	(3,453)	(488)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(162)				(162)
Dividends to preferred stockholders	(17)				(17)
Treasury stock purchased (in shares)			(14,000,000)
Treasury stock purchased	(500)					(500)
Share-based compensation plans (in shares)			0
Share-based compensation plans	11			11		0
Employee stock purchase plan shares purchased	5			5
Total comprehensive income:
Net income	449				449
Other comprehensive income	48						48
Total comprehensive income	497				449		48
Ending balance (in shares) at Sep. 30, 2019		1,000,000	444,000,000
Ending balance at Sep. 30, 2019	$ 21,851	$ 1,133	$ 6	$ 18,876	$ 6,229	$ (3,953)	$ (440)