Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Changes in Accrued Liabilities Related to Fixed Asset Additions	$ 965	$ 402
Deferred purchase price consideration related to asset acquisition included in accrued expenses	0	50
Cash flows from operating activities:
Net income (loss)	(6,410)	(9,349)
Adjustments to reconcile net loss to net cash provided by operating activities:
Provision for doubtful accounts	444	637
Depreciation and amortization	9,481	8,222
Deferred income taxes	22	0
Gain (Loss) on Disposition of Property Plant Equipment	2	21
Compensation expense related to stock-based awards and employee stock purchase plan	2,452	2,621
Unrealized currency translation gain	(290)	(205)
Changes in operating assets and liabilities:
Accounts receivable	(1,217)	1,975
Inventories	(1,907)	(896)
Prepaid expenses, other current assets, and current contract assets	(232)	(200)
Other non-current assets and non-current contract assets	(1,647)	(685)
Accounts payable	(992)	2,910
Deferred revenue, contract liabilities, and long-term contract liabilities	701	2,167
Accrued compensation, product warranty, and other	1,364	2,478
Other long-term liabilities	(10)	(305)
Net cash provided by operating activities	1,761	9,391
Cash flows from investing activities:
Capital expenditures	(11,463)	(10,234)
Cash paid for acquisition of intangible asset	(22)	(55)
Purchases of marketable securities	(2,036)	(9,351)
Maturities and sales of marketable securities	10,019	26,766
Net cash (used in) provided by investing activities	(3,502)	7,126
Cash flows from financing activities:
Repayments of long-term debt	(136)	(1,606)
Payments of employee restricted stock withholdings	0	392
Proceeds From Stock Options Exercised and Employee Stock Purchase Plan	477	1,332
Repayments of Long-term loan	3,975	8,775
Proceeds from Sale of Treasury Stock	4,500	0
Repayments of Long-term Capital Lease Obligations	(410)	0
Net cash provided by (used in) financing activities	456	(9,441)
Effect of exchange rate changes on cash and cash equivalents	(411)	1,877
Net (decrease) increase in cash and cash equivalents	(1,696)	8,953
Cash and cash equivalents at beginning of period	34,596	26,422
Cash and cash equivalents at end of period	$ 32,900	$ 35,375