Net Income Per Share - Schedule of Computation of Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net income	$ 26,340	$ 20,186	$ 18,274	$ 17,747	$ 18,196	$ 17,459	$ 64,800	$ 53,402
Denominator:
Weighted-average shares used to compute basic net income per share (in shares)	113,875			115,798			114,349	115,394
Dilutive effect of employee stock options (in shares)	7,887			10,361			8,129	11,773
Weighted-average shares used to compute diluted net income per share (in shares)	121,762			126,159			122,478	127,167
Net income per share
Basic (in dollars per share)	$ 0.23			$ 0.15			$ 0.57	$ 0.46
Diluted (in dollars per share)	$ 0.22			$ 0.14			$ 0.53	$ 0.42