Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (35,198)	$ (32,394)
Adjustments to reconcile net loss to net cash (used for)/provided by operating activities:
Depreciation and amortization	1,447	1,705
Change in fair value of warrant	0	1,162
Share-based compensation	3,330	27,305
Asset retirement obligation accretion	70	69
Amortization of intangible	26	25
Amortization of debt issuance costs and discounts	781	923
Non-cash interest expense	505
Non-cash interest income		(16)
Bad debt provision	30	31
Other, net	(15)	0
Changes in operating assets and liabilities:
Trade receivables and other receivables	(3,684)	(481)
Inventories, net	794	(334)
Prepaid expenses and other current assets	(416)	(179)
Accounts payable and accrued expenses	(1,829)	3,593
Deferred revenue	(687)	(113)
Net cash (used for)/provided by operating activities	(34,846)	1,296
Cash flows from investing activities:
Capital expenditures	(486)	(886)
Net cash used for investing activities	(486)	(886)
Cash flows used for financing activities:
Proceeds from common stock issued under employee stock purchase plan	112	0
Debt repayment	(550)	0
Payments for deferred financing costs	0	(1,528)
Payments for taxes on share-based compensation	(2,664)	(5,623)
Net cash used for financing activities	(3,102)	(7,151)
Net decrease in cash and cash equivalents	(38,434)	(6,741)
Cash and cash equivalents:
Beginning of period	60,599	17,379
End of period	22,165	10,638
Supplemental disclosures of cash flow information:
Cash payments for interest	2,577	2,970
Net (decrease)/increase in accrued capital expenditures	(313)	125
Net increase in financing costs included in accounts payable and accrued expenses	150	0
Net increase in offering costs included in accounts payable and accrued expenses	0	1,694
Accrued withholding tax for share based compensation	$ 0	$ 1,741