Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net loss	$ (12,023)	$ (6,417)	$ (66,324)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	9,853	9,887	10,183
Loss on disposal of assets			119
Financing and debt issuance costs	656		47
Accretion of debt to fair value			50,011
Stock compensation expense	5,313	5,413	8,781
Other		(139)	(31)
Changes in operating assets and liabilities:
Accounts receivable	3,089	(2,644)	838
Inventories	(6,336)	(1,635)	1,995
Prepaid expenses and other assets	(19)	(881)	(129)
Accounts payable	105	1,517	687
Accrued expenses	(2,178)	(227)	774
Deferred revenue	362	333	(303)
Other liabilities	600	152
Net cash (used in) provided by operating activities	(578)	5,359	6,648
Cash flows from investing activities:
Capital expenditures	(13,216)	(21,956)	(13,241)
Purchase of marketable securities		(2,500)
Maturity and sale of marketable securities		2,500
Net cash used in investing activities	(13,216)	(21,956)	(13,241)
Cash flows from financing activities:
Borrowings under line of credit			4,500
Repayments under line of credit			(5,500)
Repayment of borrowings under long-term debt			(18,849)
Financing costs	(656)		(47)
Proceeds from initial public offering			74,712
Repayment of obligations under capital lease	(68)	(80)	(80)
Payments made for employee restricted stock minimum tax withholdings	(200)	(238)
Proceeds from issuance of common stock			2
Net cash (used in) provided by financing activities	(924)	(318)	54,738
Net (decrease) increase in cash	(14,718)	(16,915)	48,145
Cash and cash equivalents at beginning of period	32,804	49,719	1,574
Cash and cash equivalents at end of period	18,086	32,804	49,719
Supplemental disclosures of cash flow information:
Interest paid	196	198	223
Income taxes paid	0	0	0
Supplemental disclosures of non-cash activities:
Conversion of convertible and senior convertible notes to common stock			168,510
Changes in accrued capital expenditures	$ 2,116	(5,332)	6,401
Capitalized interest			34
Capital lease		$ 21	$ 5