Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Total
Balance at Dec. 31, 2014	$ 28	$ 519,153	$ (1,218)	$ (357,383)	$ 1,276	$ 161,856
Balance (in shares) at Dec. 31, 2014	28,213
Increase (Decrease) in Stockholders' Equity
Net income				14,678		14,678
Foreign currency translation adjustments					(2,664)	(2,664)
Change in pension obligation					(43)	(43)
Exercise of stock options	$ 1	3,920				3,921
Exercise of stock options (in shares)	759
Issuance of shares under Employee Stock Purchase Plan		441				441
Issuance of shares under Employee Stock Purchase Plan (in shares)	47
Issuance of restricted common shares		(7)				(7)
Issuance of restricted common shares (in shares)	7
Stock-based compensation expense		5,582				5,582
Balance at Dec. 31, 2015	$ 29	529,089	(1,218)	(342,705)	(1,431)	183,764
Balance (in shares) at Dec. 31, 2015	29,026
Increase (Decrease) in Stockholders' Equity
Net income				11,001		11,001
Foreign currency translation adjustments					(847)	(847)
Change in pension obligation					(1)	(1)
Exercise of stock options	$ 1	2,237				2,238
Exercise of stock options (in shares)	392
Issuance of shares under Employee Stock Purchase Plan		325				325
Issuance of shares under Employee Stock Purchase Plan (in shares)	22
Issuance of restricted common shares		(11)				(11)
Issuance of restricted common shares (in shares)	108
Treasury shares returned to authorized, Value		(1,218)	$ 1,218
Treasury shares returned to authorized, Shares	(30)
Reverse stock split issuance costs		(145)				(145)
Stock-based compensation expense		5,131				5,131
Balance at Dec. 31, 2016	$ 30	535,408		(331,704)	(2,279)	201,455
Balance (in shares) at Dec. 31, 2016	29,518
Increase (Decrease) in Stockholders' Equity
Net income				126,959		126,959
Foreign currency translation adjustments					4,347	4,347
Change in pension obligation					108	108
Exercise of stock options	$ 2	15,512				15,514
Exercise of stock options (in shares)	2,358
Issuance of shares under Employee Stock Purchase Plan		845				845
Issuance of shares under Employee Stock Purchase Plan (in shares)	34
Issuance of restricted common shares		(1,164)				(1,164)
Issuance of restricted common shares (in shares)	138
Stock-based compensation expense		5,546				5,546
Balance at Dec. 31, 2017	$ 32	$ 556,147		$ (204,745)	$ 2,176	$ 353,610
Balance (in shares) at Dec. 31, 2017	32,048