Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities:
Net loss	$ (67,138)	$ (37,672)	$ (54,218)
Adjustments to reconcile net loss to net cash flows from operating activities
Depreciation	437	329	123
Accretion of debt discount and loan costs	397	500	642
Amortization of intangible assets	971	970	972
Derivative loss			13,167
Impairment loss on assets			295
Stock-based compensation expense	14,931	14,249	6,883
Changes in assets and liabilities:
Accounts receivable	(1,081)	653	(347)
Inventories	(810)	(730)	(1,828)
Prepaid expenses and other assets	(203)	(1,365)	(2,252)
Accounts payable and accrued expenses	(1,327)	5,072	4,325
Deferred revenue	(159)	14,262	3,405
Net cash flows from operating activities	(53,982)	(3,732)	(28,833)
Investing activities:
Purchase of equipment	(405)	(701)	(1,603)
Net cash flows from investing activities	(405)	(701)	(1,603)
Financing activities:
Proceeds from sales of securities, net of costs incurred	40	(40)	72,662
Proceeds from exercise of stock options	297	755	4,580
Issuance of common stock	2,460
Issuance of warrants	49
Proceeds from exercise of common stock warrants		1	7,741
Payment on note payable		(3,335)	(7,333)
Proceeds from notes payable		20,667
Return of short swing profits		6	82
Payment of deferred financing fees		(533)
Net cash flows from financing activities	2,846	17,521	77,732
Net change in cash and cash equivalents	(51,541)	13,088	47,296
Cash and cash equivalents at beginning of year	83,560	70,472	23,176
Cash and cash equivalents at end of year	32,019	83,560	70,472
Cash paid for interest	$ 2,870	$ 1,885	$ 1,386