Net Income Per Share - Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator:
Net income, basic	$ 35,146	$ 14,597	$ 51,991	$ 19,032
Add: interest expense on 2023 Notes	1,414	1,457	2,821	0
Net income, diluted	$ 36,560	$ 16,054	$ 54,812	$ 19,032
Denominator:
Weighted-average shares used to compute basic net income per share	107,614	111,359	107,468	112,005
Dilutive effect of 2023 Notes	12,189	12,602	12,189	0
Dilutive effect of options and awards granted under equity incentive plan and employee stock purchase plan	660	355	660	526
Weighted-average shares used to compute diluted net income per share	120,463	124,316	120,317	112,531
Net income per share
Basic (in dollars per share)	$ 0.33	$ 0.13	$ 0.48	$ 0.17
Diluted (in dollars per share)	$ 0.30	$ 0.13	$ 0.46	$ 0.17