Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Paid-In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Beginning balance at Dec. 31, 2016	$ 500,543	$ 998	$ 558,966	$ (63,208)	$ 129,873	$ (126,086)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(6,148)				(6,148)
Employee stock options, restricted stock and employee stock purchase plan	(185)	14	1,636		(350)	(1,485)
Stock-based compensation expense	10,843		10,843
Issuance of shares for acquisition	32,438	34	32,404
Foreign currency translation, net of tax	9,989			9,989
Ending balance at Dec. 31, 2017	547,480	1,046	603,849	(53,219)	123,375	(127,571)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	32,281				32,281
Employee stock options, restricted stock and employee stock purchase plan	777	18	3,066		(90)	(2,217)
Stock-based compensation expense	10,361		10,361
Foreign currency translation, net of tax	(14,454)			(14,454)
Ending balance at Dec. 31, 2018	569,681	1,064	617,276	(67,673)	148,802	(129,788)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(12,946)				(12,946)
Employee stock options, restricted stock and employee stock purchase plan	(425)	3	(8,290)		(1,737)	9,599
Stock-based compensation expense	11,640		11,640
Treasury shares purchased at cost	(19,031)					(19,031)
Foreign currency translation, net of tax	(274)			(274)
Ending balance at Dec. 31, 2019	$ 548,645	$ 1,067	$ 620,626	$ (67,947)	$ 134,119	$ (139,220)