Net Income per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income	$ 5,849	$ 2,409	$ 10,778	$ 5,119
Weighted Average Number of Shares Outstanding, Basic [Abstract]
Weighted-average shares of common stock outstanding	32,772	32,942	32,762	33,161
Shares used in computing basic net income per share	32,772	32,942	32,762	33,161
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Restricted stock subject to vesting	552	262	576	393
Shares issuable for acquisition consideration (in shares)	565	543	556	526
Shares used in computing diluted net income per share	33,889	33,747	33,894	34,080
Basic net income per share (in dollars per share)	$ 0.18	$ 0.07	$ 0.33	$ 0.15
Diluted net income per share (in dollars per share)	$ 0.17	$ 0.07	$ 0.32	$ 0.15
Anti-dilutive options and restricted stock not included in the calculation of diluted net income per share (in shares)	0	228	60	175
Stock Repurchase Program [Abstract]
Authorized amount to be repurchased	$ 160,000		$ 160,000		$ 135,000
Increase in authorized amount to be repurchased			25,000
Cumulative amount repurchased	$ 145,200		$ 145,200
Cumulative number of shares repurchased	12,800		12,800