Net Income Per Share Available to Common Stock - Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator:
Net income	$ 38,904	$ 23,996	$ 74,149	$ 48,488
Less: undistributed earnings allocated to participating securities	(287)	(389)	(614)	(894)
Net income attributable to common stockholders, basic	38,617	23,607	73,535	47,594
Add: undistributed earnings allocated to participating securities	18	31	38	73
Net income attributable to common stockholders, diluted	$ 38,635	$ 23,638	$ 73,573	$ 47,667
Denominator:
Weighted-average shares used in computing net income per share available to common stockholders, basic (in shares)	68,275	65,524	68,006	65,018
Add weighted-average effect of dilutive securities:
Stock options and RSAs (in shares)	4,488	5,497	4,466	5,708
Employee stock purchase plan (in shares)	54	194	51	193
Weighted-average shares used in computing net income per share available to common stockholders, diluted (in shares)	72,817	71,215	72,523	70,919
Net income per share attributable to common stockholders:
Basic (usd per share)	$ 0.57	$ 0.36	$ 1.08	$ 0.73
Diluted (usd per share)	$ 0.53	$ 0.33	$ 1.01	$ 0.67