Earnings Per Share - Reconciliation of Weighted Average Number of Shares of Common Stock Outstanding In Calculating EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Net income	$ 55	$ 74	$ 119	$ 195
Denominator:
Weighted average shares used to compute Basic EPS	145,678	144,133	145,618	143,662
Weighted average effect of dilutive securities:
Stock options	1,135	1,442	1,229	1,959
RSUs	404	253	314	265
Weighted average shares used to compute Diluted EPS	147,217	145,828	147,161	145,886
Basic EPS	$ 0.38	$ 0.51	$ 0.82	$ 1.35
Diluted EPS	$ 0.37	$ 0.51	$ 0.81	$ 1.34