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	$ (15,325)	$ (7,317)	$ (16,260)
Adjustments to reconcile net loss to net cash flow from operating activities:
Depreciation and amortization	33,754	32,637	30,715
Stock-based compensation	11,537	10,117	12,598
Other	2,131	2,445	1,302
Changes in operating assets and liabilities:
Accounts receivable	1,056	(7,388)	(1,130)
Inventory	(22,917)	(31,069)	(12,113)
Prepaid expenses and other assets	(1,045)	(68)	(77)
Accounts payable	(22)	3,532	(2,775)
Accrued expenses and other liabilities	(1,774)	4,141	635
Deferred revenues	(2,593)	(2,443)	(2,353)
Net cash provided by operating activities	4,802	4,587	10,542
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	(100)	(513)	0
Purchase of cost method investment	(2,500)	0	0
Proceeds from sales of marketable securities	0	0	676
Purchases of property and equipment	(9,194)	(8,848)	(11,537)
Net cash used in investing activities	(11,794)	(9,361)	(10,861)
Cash flows from financing activities:
Issuance of shares under stock incentive plans, net of payroll taxes paid	12,003	5,994	6,663
Investment by noncontrolling interest holder	0	1,255	929
Proceeds from loans, lines of credit and capital leases	452	0	1,275
Repayments on loans and lines of credit	(164)	(384)	(143)
Repayments on capital leases	(1,306)	(1,590)	(1,391)
Net cash provided by financing activities	10,985	5,275	7,333
Foreign exchange effect on cash and cash equivalents	1,303	66	(833)
Increase in cash and cash equivalents	5,296	567	6,181
Cash and cash equivalents, beginning of year	59,632	59,065	52,884
Cash and cash equivalents, end of year	$ 64,928	$ 59,632	$ 59,065