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, 2016	$ 500,543	$ 998	$ 558,966	$ (63,208)	$ 129,873	$ (126,086)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(983)				(983)
Employee stock options, restricted stock and employee stock purchase plan	442	1	202		(186)	425
Stock-based compensation expense	2,836		2,836
Foreign currency translation	2,555			2,555
Ending balance at Mar. 31, 2017	505,393	999	562,004	(60,653)	128,704	(125,661)
Beginning balance at Dec. 31, 2017	547,480	1,046	603,849	(53,219)	123,375	(127,571)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting changes	(6,764)
Net income (loss)	7,222				7,222
Employee stock options, restricted stock and employee stock purchase plan	654	0	353		(90)	391
Stock-based compensation expense	2,289		2,289
Foreign currency translation	(666)			(666)
Ending balance at Mar. 31, 2018	$ 550,215	$ 1,046	$ 606,491	$ (53,885)	$ 123,743	$ (127,180)