Consolidated Statements of Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Total
Balance at Dec. 31, 2011	$ 107	$ 499,332	$ (1,218)	$ (288,443)	$ 4,777	$ 214,555
Balance (in shares) at Dec. 31, 2011	106,809
Increase (Decrease) in Stockholders' Equity
Net loss				(34,034)		(34,034)
Foreign currency translation adjustments					642	642
Change in pension obligation					(399)	(399)
Exercise of stock options	1	967				968
Exercise of stock options (in shares)	1,148
Issuance of shares under Employee Stock Purchase Plan		390				390
Issuance of shares under Employee Stock Purchase Plan (in shares)	306
Issuance of restricted common shares		(22)				(22)
Issuance of restricted common shares (in shares)	30
Stock-based compensation expense		3,976				3,976
Balance at Dec. 31, 2012	108	504,643	(1,218)	(322,477)	5,020	186,076
Balance (in shares) at Dec. 31, 2012	108,293
Increase (Decrease) in Stockholders' Equity
Net loss				(17,144)		(17,144)
Foreign currency translation adjustments					695	695
Change in pension obligation					24	24
Exercise of stock options	2	1,667				1,669
Exercise of stock options (in shares)	1,511
Issuance of shares under Employee Stock Purchase Plan		436				436
Issuance of shares under Employee Stock Purchase Plan (in shares)	206
Issuance of restricted common shares		(26)				(26)
Issuance of restricted common shares (in shares)	215
Stock-based compensation expense		4,272				4,272
Balance at Dec. 31, 2013	110	510,992	(1,218)	(339,621)	5,739	176,002
Balance (in shares) at Dec. 31, 2013	110,225
Increase (Decrease) in Stockholders' Equity
Net loss				(11,266)		(11,266)
Foreign currency translation adjustments					(4,150)	(4,150)
Change in pension obligation					(313)	(313)
Exercise of stock options	3	2,892				2,895
Exercise of stock options (in shares)	2,418
Issuance of shares under Employee Stock Purchase Plan		446				446
Issuance of shares under Employee Stock Purchase Plan (in shares)	199
Issuance of restricted common shares		(7)				(7)
Issuance of restricted common shares (in shares)	7
Stock-based compensation expense		4,745				4,745
Balance at Dec. 31, 2014	$ 113	$ 519,068	$ (1,218)	$ (350,887)	$ 1,276	$ 168,352
Balance (in shares) at Dec. 31, 2014	112,849