Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities
Net loss	$ (43,414)	$ (109,513)
Adjustments to reconcile net loss to cash flows used in operating activities:
Stock-based compensation expense	8,653	7,336
Amortization of debt discount	1,316	62,965
Change in fair value of derivative liability	0	(225)
Depreciation and amortization	476	459
Amortization of deferred lease incentive	(123)	(122)
Write-down of inventory to net realizable value	5,288	335
Deferred income taxes	(635)	39
Changes in operating assets and liabilities:
Other current assets	598	(5,466)
Accounts receivable, net	(7,284)	(3,223)
Inventory	(24,516)	(4,683)
Other assets	(3,155)	9
Other current liabilities	13	14
Accounts payable and accrued expenses	8,073	7,988
Other liabilities	(83)	(70)
Net cash used in operating activities	(54,793)	(44,157)
Cash flows from investing activities
Purchases of property, plant and equipment	(52)	(420)
Net cash used in investing activities	(52)	(420)
Cash flows from financing activities
Proceeds from issuance of common stock, net of commission	0	73,125
Proceeds from issuance of convertible senior notes	10,000	0
Payments for common stock issuance costs	0	(88)
Proceeds from exercise of stock options	777	257
Net cash provided by financing activities	10,777	73,294
Net (decrease) increase in cash and cash equivalents	(44,068)	28,717
Cash and cash equivalents at beginning of the period	93,526	111,810
Cash and cash equivalents at end of the period	49,458	140,527
Non-cash financing activities:
Change in fair value of conversion feature	6,228	0
Reclassification of derivative liability to equity	$ 0	$ 62,735