Stockholders' Equity - Changes in Equity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 831	$ 1,180
Total comprehensive income (loss)	90	(8)
Common stock dividends	(9)	(8)
Distributions to noncontrolling interests	(1)	(1)
Common stock share repurchases	(28)	(63)
Derecognition of noncontrolling interests	0	(5)
Stock compensation	2	4
Stock withheld for employee taxes	(1)	(2)
Ending Balance	884	1,097
Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	728	1,080
Total comprehensive income (loss)	86	(20)
Common stock dividends	(9)	(8)
Common stock share repurchases	(28)	(63)
Stock compensation	2	4
Stock withheld for employee taxes	(1)	(2)
Ending Balance	778	991
Attributable to Non-Controlling Interests [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	103	100
Total comprehensive income (loss)	4	12
Distributions to noncontrolling interests	$ (1)	(1)
Derecognition of noncontrolling interests		(5)
Ending Balance	$ 106	$ 106