Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating activities
Net loss	$ (96,313)	$ (90,411)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	5,574	5,320
Stock-based compensation	10,138	8,406
Premium amortization and discount accretion on investment securities	264	703
Amortization of debt discount	293	51
Interest accrued for borrowings and claims related settlement	189	1,825
Inventory excess adjustments	230	413
(Gain) loss on disposal of property and equipment	(12)	12
Impairment of assets	1,544	576
Loss on investments	42	55
Loss from changes in fair value of warrants	4,119	397
Provision for doubtful accounts	152	(93)
Changes in operating assets and liabilities
Accounts receivable	(16,460)	5,746
Inventory	(3,477)	(3,187)
Prepaid expenses and other current assets	2,371	660
Other assets	302	476
Accounts payable	967	(4,548)
Accrued compensation	(13)	(1,639)
Other accrued liabilities	(3,798)	3,724
Deferred revenue	36,586	467
Deferred rent, net of current portion	(466)	1,351
Net cash used in operating activities	(57,768)	(69,696)
Investing activities
Purchases of investments	(115,066)	(184,263)
Proceeds from sale of investments	37,387	55,352
Proceeds from maturity of investments	52,600	124,325
Purchases of property and equipment, net	(1,770)	(9,147)
Net cash used in investing activities	(26,849)	(13,733)
Financing activities
Proceeds from exercise of stock options	12,063	1,834
Proceeds from issuance of common stock under employee stock purchase plan	1,855	1,503
Proceeds from equity offering, net of issuance costs	96,777
Borrowings under long-term debt facility		75,000
Net cash provided by financing activities	110,695	78,337
Net increase (decrease) in cash, cash equivalents and restricted cash	26,078	(5,092)
Cash, cash equivalents and restricted cash, beginning of period	13,021	16,690
Cash, cash equivalents and restricted cash, end of period	$ 39,099	$ 11,598