Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net loss	$ (6,281)	$ (8,055)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	7,298	7,422
Stock-compensation expense	4,277	4,175
Settlement of asset retirement obligation		(14)
Postponed financing costs	656
Changes in operating assets and liabilities:
Accounts receivable	999	(5,425)
Inventories	(6,370)	(1,732)
Prepaid expenses and other assets	189	(1,001)
Accounts payable	(17)	1,504
Accrued expenses	(2,189)	(1,123)
Deferred revenue	72	4,167
Net cash used in operating activities	(1,366)	(82)
Cash flows from investing activities:
Capital expenditures	(9,994)	(19,377)
Purchases of marketable securities		(2,500)
Maturity and sale of marketable securities		2,500
Net cash used in investing activities	(9,994)	(19,377)
Cash flows from financing activities:
Repayment of obligations under capital lease	(55)	(58)
Payments made for employee restricted stock tax withholdings	(196)	(238)
Payment of deferred financing costs	(64)
Net cash used in financing activities	(315)	(296)
Net decrease in cash	(11,675)	(19,755)
Cash at beginning of period	32,804	49,719
Cash at end of period	21,129	29,964
Supplemental disclosures of cash flow information:
Interest paid	153	149
Income taxes paid	0	0
Supplemental disclosures of non-cash activities:
Changes in accrued capital expenditures	602	(6,112)
Changes in building lease incentives	268
Advanced billings		1,142
Unpaid financing costs	(592)
Capitalized leases		$ 21
Settlement of asset retirement obligation	$ 241