Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net loss	$ (45,498)	$ (30,933)	$ (15,282)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,782	817	286
Amortization of intangible assets	10	71	77
Amortization of investment discount	188	269	76
Equity-based compensation	8,388	9,624	3,828
Impairment loss	0	3	11
(Increase) decrease in assets:
Accounts receivable	1	(54)	739
Prepaid expense and other	(1,241)	(166)	(114)
Other current assets	(12)	0	0
Increase (decrease) in liabilities:
Accounts payable	329	1,336	205
Accrued liabilities	827	80	(356)
Deferred revenue and income	100	168	781
Net cash used in operating activities	(35,126)	(18,785)	(9,749)
Cash flows from investing activities:
Purchases of equipment	(3,656)	(1,933)	(1,158)
Purchase of available-for-sale securities	(12,418)	(7,657)	(12,014)
Sales of available-for-sale securities	141	861	0
Maturity of available-for-sale securities	13,258	5,357	0
Net cash used in investing activities	(2,675)	(3,372)	(13,172)
Cash flows from financing activities:
Exercise of warrants and options	805	923	20,969
Issuance of common stock and warrants	104,165	44,875	19,912
Payments on capital lease obligations	(147)	(107)	0
Net cash provided by financing activities	104,823	45,691	40,881
Increase in cash and cash equivalents	67,022	23,534	17,960
Cash and cash equivalents, beginning of period	53,563	30,029	12,069
Cash and cash equivalents, end of period	$ 120,585	$ 53,563	$ 30,029