Net Income per Share - Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net income	$ 6,305	$ 7,027	$ 17,083	$ 12,146
Weighted Average Number of Shares Outstanding, Basic [Abstract]
Weighted-average shares of common stock outstanding	32,648	32,673	32,724	32,997
Shares used in computing basic net income per share	32,648	32,673	32,724	32,997
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Restricted stock subject to vesting	733	459	665	450
Shares issuable for acquisition consideration (in shares)	264	859	457	638
Shares used in computing diluted net income per share	33,645	33,991	33,846	34,085
Basic net income per share (in dollars per share)	$ 0.19	$ 0.22	$ 0.52	$ 0.37
Diluted net income per share (in dollars per share)	$ 0.19	$ 0.21	$ 0.50	$ 0.36