CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net loss	$ (55,868)	$ (38,755)	$ (43,337)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,699	1,415	745
Stock-based compensation	6,730	5,153	3,268
Changes in valuation of warrant liability	(3,566)	(7,708)	15,099
Non-cash interest expense (income)	508	131	(25)
Non-cash deferred manufacturing and development expense	434
Deferred income taxes	7	26	27
Loss on disposal of fixed assets		3	56
Tax benefit from other unrealized gain on available-for-sale securities	(3,825)
Changes in operating assets and liabilities:
Accounts receivable	(301)	632	(1,681)
Inventories	3,991	3,033	(1,813)
Other assets	1,379	(1,655)	286
Accounts payable	(3,866)	(973)	(1,512)
Accrued liabilities	1,359	(1,382)	2,121
Deferred revenue	190	269	104
Net cash used in operating activities	(51,129)	(39,811)	(26,662)
Investing activities
Capital expenditures	(722)	(2,106)	(663)
Purchases of investments	(90,407)	(25,981)	(30,146)
Proceeds from maturities of investments	92,645	24,915	1,631
Restricted cash	(104)	(175)	(14)
Net cash provided by (used in) investing activities	1,412	(3,347)	(29,192)
Financing activities
Net proceeds from exercise/purchase of equity incentives and warrants	12,767	11,592	1,684
Net proceeds from public offering	75,300	18,488	61,425
Proceeds from debt, net of discount	10,000	9,848	3,102
Repayment of debt	(113)	(3,474)	(7,568)
Net cash provided by financing activities	97,954	36,454	58,643
Net increase (decrease) in cash and cash equivalents	48,237	(6,704)	2,789
Cash and cash equivalents, beginning of year	22,781	29,485	26,696
Cash and cash equivalents, end of year	71,018	22,781	29,485
Supplemental disclosures:
Cash paid for interest	1,087	563	294
Cash paid for income taxes	153	$ 177	146
Non-cash settlement of warranty claim			$ 1,272
Unpaid manufacturing and development obligation	$ 7,051