Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Paid-In Capital	Accumulated Other Comprehensive Loss	Retained Earnings	Treasury Stock
Beginning 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)	1,282				1,282
Employee stock options, restricted stock and employee stock purchase plan	790		309			481
Stock-based compensation expense	4,969		4,969
Treasury shares purchased at cost	(5,013)					(5,013)
Foreign currency translation, net of tax	(1,921)			(1,921)
Ending balance at Mar. 31, 2019	569,788	1,064	622,554	(69,594)	150,084	(134,320)
Beginning balance at Dec. 31, 2019	548,645	1,067	620,626	(67,947)	134,119	(139,220)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(12,148)				(12,148)
Employee stock options, restricted stock and employee stock purchase plan	498		(103)		(735)	1,336
Stock-based compensation expense	1,592		1,592
Foreign currency translation, net of tax	(7,493)			(7,493)
Ending balance at Mar. 31, 2020	$ 530,359	$ 1,067	$ 622,115	$ (75,440)	$ 120,501	$ (137,884)