CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) shares in Millions, $ 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, 2013		0.0	560.0
Beginning balance at Dec. 31, 2013	$ 19,196	$ 0	$ 6	$ 18,603	$ 1,235	$ 0	$ (648)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders	(806)				(806)
Treasury stock purchased (in shares)			(14.0)
Treasury stock purchased	(334)					(334)
Share-based compensation plans	69			71		(2)
Employee stock purchase plan shares purchased	2			2
Total comprehensive income:
Net income	865				865
Other comprehensive income (loss)	276						276
Total comprehensive income	1,141				865		276
Ending balance (in shares) at Dec. 31, 2014		0.0	546.0
Ending 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	(214)				(214)
Dividends to preferred stockholders	(7)				(7)
Issuance of preferred stock (in shares)		0.0
Issuance of preferred stock	$ 247	$ 247
Treasury stock purchased (in shares)	(20.1)		(20.0)
Treasury stock purchased	$ (500)					(500)
Share-based compensation plans (in shares)			2.0
Share-based compensation plans	18			40		(22)
Employee stock purchase plan shares purchased	9			9
Total comprehensive income:
Net income	840				840
Other comprehensive income (loss)	(15)						(15)
Total comprehensive income	825				840		(15)
Ending balance (in shares) at Dec. 31, 2015		0.0	528.0
Ending 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	(241)				(241)
Dividends to preferred stockholders	$ (14)				(14)
Treasury stock purchased (in shares)	(17.3)		(17.0)
Treasury stock purchased	$ (430)			(25)		(405)
Share-based compensation plans (in shares)			1.0
Share-based compensation plans	12			12		0
Employee stock purchase plan shares purchased	10			10
Total comprehensive income:
Net income	1,045				1,045
Other comprehensive income (loss)	(281)						(281)
Total comprehensive income	764				1,045		(281)
Ending balance (in shares) at Dec. 31, 2016		0.0	512.0
Ending balance at Dec. 31, 2016	$ 19,747	$ 247	$ 6	$ 18,722	$ 2,703	$ (1,263)	$ (668)