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		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Net income	$ 51,257	$ 28,690	$ 125,406	$ 77,178
Less: undistributed earnings allocated to participating securities	(295)	(389)	(931)	(1,314)
Net income attributable to common stockholders, basic	50,962	28,301	124,475	75,864
Add: undistributed earnings allocated to participating securities	18	28	56	103
Net income attributable to common stockholders, diluted	$ 50,980	$ 28,329	$ 124,531	$ 75,967
Denominator:
Weighted-average shares used in computing net income per share available to common stockholders, basic (in shares)	69,076	66,629	68,365	65,609
Add weighted-average effect of dilutive securities:
Stock options and RSUs (in shares)	4,357	5,163	4,429	5,529
Employee stock purchase plan (in shares)	20	95	17	94
Weighted-average shares used in computing net income per share available to common stockholders, diluted (in shares)	73,453	71,887	72,811	71,232
Net income per share attributable to common stockholders:
Basic (in usd per share)	$ 0.74	$ 0.42	$ 1.82	$ 1.16
Diluted (in usd per share)	$ 0.69	$ 0.39	$ 1.71	$ 1.07