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 Income (Loss)
Beginning balance (in shares) at Dec. 31, 2014		0	546,000,000
Beginning balance at Dec. 31, 2014	$ 19,268	$ 0	$ 6	$ 18,676	$ 1,294	$ (336)	$ (372)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(161)				(161)
Dividends to preferred stockholders	(7)				(7)
Issuance of preferred stock (in shares)		0
Issuance of preferred stock	247	$ 247
Treasury stock purchased (in shares)			(20,000,000)
Treasury stock purchased	(500)					(500)
Share-based compensation plans (in shares)			2,000,000
Share-based compensation plans	14			35		(21)
Employee stock purchase plan shares purchased	7			7
Total comprehensive income:
Net income	619				619
Other comprehensive income	113						113
Total comprehensive income	732				619		113
Ending balance (in shares) at Sep. 30, 2015		0	528,000,000
Ending balance at Sep. 30, 2015	19,600	$ 247	$ 6	18,718	1,745	(857)	(259)
Beginning balance at Jun. 30, 2015							(359)
Total comprehensive income:
Other comprehensive income							100
Total comprehensive income	320
Ending balance (in shares) at Sep. 30, 2015		0	528,000,000
Ending balance at Sep. 30, 2015	19,600	$ 247	$ 6	18,718	1,745	(857)	(259)
Beginning balance (in shares) at Dec. 31, 2015		0	528,000,000
Beginning balance at Dec. 31, 2015	19,646	$ 247	$ 6	18,725	1,913	(858)	(387)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(179)				(179)
Dividends to preferred stockholders	(14)				(14)
Treasury stock purchased (in shares)			(11,000,000)
Treasury stock purchased	(250)					(250)
Share-based compensation plans (in shares)			1,000,000
Share-based compensation plans	8			8		0
Employee stock purchase plan shares purchased	7			7
Total comprehensive income:
Net income	763				763
Other comprehensive income	200						200
Total comprehensive income	963				763		200
Ending balance (in shares) at Sep. 30, 2016		0	518,000,000
Ending balance at Sep. 30, 2016	20,181	$ 247	$ 6	18,740	2,483	(1,108)	(187)
Beginning balance at Jun. 30, 2016							(159)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to preferred stockholders	$ (7)
Treasury stock purchased (in shares)	(11,062,192)
Total comprehensive income:
Other comprehensive income							(28)
Total comprehensive income	$ 269
Ending balance (in shares) at Sep. 30, 2016		0	518,000,000
Ending balance at Sep. 30, 2016	$ 20,181	$ 247	$ 6	$ 18,740	$ 2,483	$ (1,108)	$ (187)