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		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator:
Net income	$ 34	$ 58	$ 62	$ 121
Denominator:
Weighted average shares used to compute Basic EPS	145,732	143,709	145,588	143,427
Weighted average effect of dilutive securities:
Stock options	1,060	2,019	1,123	2,218
RSUs	268	231	271	271
Weighted average shares used to compute Diluted EPS	147,060	145,959	146,982	145,916
Basic EPS	$ 0.23	$ 0.40	$ 0.42	$ 0.85
Diluted EPS	$ 0.23	$ 0.40	$ 0.42	$ 0.83