Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Operating Activities
Net loss	$ (34,939)	$ (28,232)
Adjustments to reconcile net loss to net cash used in operating activities:
Loss/(Gain) from change in fair value of derivative warrant liability	4,171	2,361
Loss/(Gain) from change in fair value of the 2017 Notes	3,629	(3,582)
Loss/(Gain) on exchange or conversion of debt	920	(285)
Loss/(Gain) on extinguishment of warrant liability	918	(1,775)
Loss/(Gain) on issuance of equity	1,519
Stock-based compensation	812	1,953
Depreciation and amortization	5,038	4,897
Non-cash interest expense	3,339	2,740
Changes in operating assets and liabilities:
Accounts receivable	312	1,227
Inventories	284	1,589
Prepaid expenses and other current assets	(113)	114
Accounts payable, accrued expenses, and long-term liabilities	(2,095)	(2,019)
Net cash used in operating activities	(16,205)	(21,012)
Investing Activities
Acquisitions of property, plant and equipment	(5,520)	(271)
Proceeds from sales tax refund for property, plant and equipment		144
Net cash used in investing activities	(5,520)	(127)
Financing Activities
Payments on secured debt	(504)	(236)
Debt and equity offering costs	(3,295)	(2,785)
Proceeds from issuance of common stock upon exercise of stock options and employee stock purchase plan		3
Proceeds from issuance of common stock and common stock units	28,661	23,850
Proceeds from the exercise of warrants	10,895	10,151
Net cash provided by financing activities	35,757	30,983
Net increase in cash and cash equivalents	14,032	9,844
Cash and cash equivalents
Beginning of period	17,031	6,359
End of period	31,063	16,203
Supplemental disclosures of cash and non-cash investing and financing transactions
Cash paid for interest, net of interest capitalized	3,102	3,449
Non-cash purchase of property, plant and equipment	140	131
Conversion of convertible debt to common stock	11,400	2,000
Sale of common stock shares (public offering)	13,023
2015 Warrants | Series A Warrant
Supplemental disclosures of cash and non-cash investing and financing transactions
Warrant issuance		1,437
2015 Warrants | Series B Warrant
Supplemental disclosures of cash and non-cash investing and financing transactions
Warrant issuance		2,528
2015 Warrants | Series C Warrant
Supplemental disclosures of cash and non-cash investing and financing transactions
Warrant issuance		$ 1,299
2016 Warrants | Series F Warrant
Supplemental disclosures of cash and non-cash investing and financing transactions
Warrant issuance	2,162
2016 Warrants | Series G Warrant
Supplemental disclosures of cash and non-cash investing and financing transactions
Warrant issuance	1,577
2016 Warrants | Series H Warrant
Supplemental disclosures of cash and non-cash investing and financing transactions
Warrant issuance	2,146
2016 Warrants | Series I Warrant
Supplemental disclosures of cash and non-cash investing and financing transactions
Warrant issuance	5,747
2016 Warrants | Series J Warrant
Supplemental disclosures of cash and non-cash investing and financing transactions
Warrant issuance	$ 1,776