Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net (loss) income	$ (11,034)	$ (7,517)	$ 2,253
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Provision for doubtful accounts	674	872	1,337
Depreciation and amortization	11,037	12,564	12,719
Deferred income taxes	(756)	2,406	(411)
Loss (gain) on disposals of fixed assets	27	907	(4)
Unrealized gain (loss) on derivative instruments	0	0	57
Compensation expense related to stock-based awards and employee stock purchase plan	3,518	3,651	3,734
Foreign Currency Transaction Gain (Loss), Unrealized	(86)	881	391
Changes in operating assets and liabilities:
Accounts receivable	2,701	10,709	(5,803)
Inventories	(1,978)	806	(3,755)
Prepaid expenses and other current assets	1,045	(332)	(1,576)
Other non-current assets	(712)	(2,378)	1,539
Accounts payable	6,711	(790)	(3,390)
Deferred revenue	(138)	1,474	(1,643)
Accrued expenses	834	(3,687)	3,023
Other long-term liabilities	(316)	(867)	(74)
Net cash provided by operating activities	11,527	18,699	8,397
Cash flows from investing activities:
Capital expenditures	(12,788)	(5,631)	(5,694)
Payments to Acquire Intangible Assets	(83)	0	0
Purchases of marketable securities	(11,115)	(13,173)	(11,323)
Maturities and sales of marketable securities	28,508	10,080	13,217
Net cash provided by (used in) investing activities	4,522	(8,724)	(3,800)
Cash flows from financing activities:
Repayments of long-term debt	(1,649)	(1,358)	(1,307)
Repayments of Long-term loan	(9,350)	(5,281)	(4,876)
Proceeds from stock options exercised and employee stock purchase plan	1,644	2,583	432
Payment of employee restricted stock withholdings	(392)	(313)	(578)
Other	0	(4)	0
Net cash used in financing activities	(9,747)	(4,373)	(6,329)
Effect of exchange rate changes on cash and cash equivalents	1,872	(1,899)	(838)
Net increase (decrease) in cash and cash equivalents	8,174	3,703	(2,570)
Cash and cash equivalents at beginning of period	26,422	22,719	25,289
Cash and cash equivalents at end of period	34,596	26,422	22,719
Supplemental disclosure of cash flow information:
Cash paid for interest	1,449	1,433	1,467
Cash paid for income taxes, net of refunds	972	3,647	2,182
Changes in Accrued Liabilities Related to Fixed Asset Additions	501	345	0
Deferred purchase price consideration related to asset acquisition included in accrued expenses	$ 50	$ 0	$ 0