Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income
Beginning balance, shares at Dec. 31, 2014		29,846
Beginning balance at Dec. 31, 2014	$ 126,953	$ 2,982	$ 277,314	$ (158,066)	$ 4,723
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee benefit plans, shares		142
Common stock issued under employee benefit plans	875	$ 14	861
Share-based compensation, shares		80
Share-based compensation	3,946	$ 8	3,938
Proceeds from issuance of common stock, net, shares		1,831
Proceeds from issuance of common stock, net	9,564	$ 183	9,381
Cancellation of restricted shares, shares		(117)
Cancellation of restricted shares	0	$ (11)	11
Issuance of common stock for acquisiton	0
Net loss	(22,333)			(22,333)
Foreign currency translation adjustments	1,574				1,574
Pension adjustment, net of tax provision (benefit)	(1,403)				(1,403)
Ending balance, shares at Dec. 31, 2015		31,782
Ending balance at Dec. 31, 2015	119,176	$ 3,176	291,505	(180,399)	4,894
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee benefit plans, shares		180
Common stock issued under employee benefit plans	841	$ 18	823
Share-based compensation, shares		225
Share-based compensation	4,004	$ 21	3,983
Proceeds from issuance of common stock, net, shares		1,830
Cancellation of restricted shares, shares		(52)
Cancellation of restricted shares	0	$ (5)	5
Issuance of common stock for acquisiton	0
Net loss	(23,705)			(23,705)
Foreign currency translation adjustments	(2,107)				(2,107)
Pension adjustment, net of tax provision (benefit)	2,613				2,613
Ending balance, shares at Dec. 31, 2016		32,135
Ending balance at Dec. 31, 2016	100,822	$ 3,210	296,316	(204,104)	5,400
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee benefit plans, shares		78
Common stock issued under employee benefit plans	326	$ 7	319
Share-based compensation, shares		536
Share-based compensation	5,945	$ 54	5,891
Cancellation of restricted shares, shares		(10)
Cancellation of restricted shares	(13)	$ 0	(13)
Issuance of common stock for bonuses and director fees, shares		314
Issuance of common stock for bonuses and director fees	1,803	$ 31	1,772
Issuance of common stock for acquisition, shares		4,147
Issuance of common stock for acquisiton	25,294	$ 415	24,879
Equity component of convertible senior notes issued	8,377		8,377
Net loss	(43,129)			(43,129)
Foreign currency translation adjustments	5,131				5,131
Pension adjustment, net of tax provision (benefit)	1,545				1,545
Ending balance, shares at Dec. 31, 2017		37,200
Ending balance at Dec. 31, 2017	$ 106,101	$ 3,717	$ 337,541	$ (247,233)	$ 12,076