Business Combinations - Pro Forma Results of Operations (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Business Combinations [Abstract]
Revenues	$ 513,573	$ 531,517
Net income	$ 28,949	$ 21,581
Basic net income per share (in dollars per share)	$ 0.88	$ 0.64
Diluted net income per share (in dollars per share)	$ 0.86	$ 0.62
Shares used in computing basic net income per share (in shares)	32,748	33,513
Shares used in computing diluted net income per share (in shares)	33,618	34,550