Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net loss	$ (8,232)	$ (11,034)	$ (7,517)
Adjustments to reconcile net loss to net cash provided by operating activities:
Provision for doubtful accounts	657	674	872
Depreciation and amortization	12,857	11,037	12,564
Deferred income taxes	(781)	(756)	2,406
Loss on disposals of fixed assets	17	27	907
Compensation expense related to stock-based awards and employee stock purchase plan	3,321	3,518	3,651
Unrealized currency translation (gain) loss	(377)	(86)	881
Changes in operating assets and liabilities:
Accounts receivable	(2,183)	2,701	10,709
Inventories	(174)	(1,978)	806
Prepaid expenses, other current assets, and current contract assets	(286)	1,045	(332)
Other non-current assets and non-current contract assets	(2,054)	(712)	(2,378)
Accounts payable	2,041	6,711	(790)
Deferred revenue, contract liabilities, and long-term contract liabilities	(498)	(138)	1,474
Accrued compensation, product warranty, and other	874	834	(3,687)
Other long-term liabilities	2	(316)	(867)
Net cash provided by operating activities	5,184	11,527	18,699
Cash flows from investing activities:
Capital expenditures	(15,897)	(12,788)	(5,631)
Cash paid for acquisition of intangible assets	(44)	(83)	0
Purchases of marketable securities	(2,036)	(11,115)	(13,173)
Maturities and sales of marketable securities	10,330	28,508	10,080
Net cash (used in) provided by investing activities	(7,647)	4,522	(8,724)
Cash flows from financing activities:
Repayments of long-term debt	(182)	(1,649)	(1,358)
Repayments of term note borrowings	(22,507)	(9,350)	(5,281)
Proceeds from stock options exercised and employee stock purchase plan	484	1,644	2,583
Payment of employee restricted stock withholdings	0	(392)	(313)
Proceeds from line of credit borrowings	5,000	0	0
Sale of treasury stock	4,500	0	0
Payment of capital lease	(561)	0	0
Other	0	0	(4)
Net cash used in financing activities	(13,266)	(9,747)	(4,373)
Effect of exchange rate changes on cash and cash equivalents	(817)	1,872	(1,899)
Net (decrease) increase in cash and cash equivalents	(16,546)	8,174	3,703
Cash and cash equivalents at beginning of period	34,596	26,422	22,719
Cash and cash equivalents at end of period	18,050	34,596	26,422
Supplemental disclosure of cash flow information:
Cash paid for interest	1,679	1,449	1,433
Cash paid for income taxes, net of refunds	2,578	972	3,647
Changes in accrued other and accounts payable related to property and equipment additions	244	501	345
Deferred purchase price consideration related to asset acquisition included in accrued expenses	0	50	0
Satellite hubs acquired under capital lease	$ 3,068	$ 0	$ 0