Business Combinations, Pro Forma Results of Operations (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Business Combinations [Abstract]
Revenues	$ 496,085	$ 515,416
Net income	$ 25,898	$ 26,815
Basic net income per share (in dollars per share)	$ 0.76	$ 0.81
Diluted net income per share (in dollars per share)	$ 0.75	$ 0.78
Shares used in computing basic net income per share (in shares)	33,896	33,212
Shares used in computing diluted net income per share (in shares)	34,571	34,381