Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Operating Activities
Net loss	$ (31,841)	$ (29,685)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,428	2,974
Amortization of premium on investment securities	761
Gain on sales of property and equipment		(5)
Impairment of assets	20
Non-cash interest accrual	237
Gain on investments	(112)
Stock based compensation	5,292	2,740
Loss from changes in fair value of warrants	306	3,925
Loss from change in fair value of long term debt		2,122
Provision for doubtful accounts	479	119
Changes in operating assets and liabilities
Accounts receivable	(789)	549
Inventory	(800)	(3,091)
Prepaid expenses and other current assets	(296)	(2,223)
Restricted cash	(32)	(262)
Other assets	(532)	(337)
Accounts payable	2,150	2,678
Accrued compensation	543	1,031
Other accrued liabilities	(156)	3,683
Deferred revenue	188	(78)
Deferred rent	1,964
Net cash used in operating activities	(20,190)	(15,860)
Investing Activities
Purchases of investments	(30,118)
Proceeds from sale of investments	16,766
Proceeds from maturity of investments	18,000
Proceeds from sale of property and equipment	225
Purchases of property and equipment, net	(7,311)	(6,037)
Net cash used in investing activities	(2,438)	(6,037)
Financing Activities
Proceeds from issuance of common stock, net of issuance costs	970	315
Proceeds from exercise of stock options	2,268
Borrowings under credit facility	8,000
Repayment under credit facility	(1,000)
Proceeds from issuance of preferred stock, net		(27)
Costs paid for loan		(6)
Repayments of equipment financing		(1,170)
Proceeds from collection of officer receivable		192
Deferred offering costs		(2,340)
Net cash provided by (used in) financing activities	10,238	(3,036)
Net decrease in cash	(12,390)	(24,933)
Cash at beginning of period	28,947	87,176
Cash at end of period	$ 16,557	$ 62,243