Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities
Net loss	$ (32,873)	$ (33,480)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,860	1,758
Stock-based compensation	3,154	2,543
Premium amortization and discount accretion on investment securities	144	269
Amortization of debt discount	98
Inventory excess adjustments	45	145
Loss on disposal of property and equipment		12
Impairment of assets	1,544	576
Non-cash interest accrual	13	184
Loss on investments	32	40
Loss (gain) from changes in fair value of warrants	108	(1,042)
Provision for doubtful accounts	48	(101)
Changes in operating assets and liabilities
Accounts receivable	(6,284)	3,538
Inventory	(2,959)	(1,954)
Prepaid expenses and other current assets	2,524	(810)
Other assets	215	165
Accounts payable	51	(1,902)
Accrued compensation	333	(1,739)
Other accrued liabilities	(2,799)	5,612
Deferred revenue	35,485	18
Deferred rent, net of current portion	307	1,548
Net cash provided by (used in) operating activities	1,046	(24,620)
Investing activities
Purchases of investments	(9,986)	(3,995)
Proceeds from sale of investments	27,896	25,053
Proceeds from maturity of investments	8,000	3,000
Purchases of property and equipment, net	(852)	(6,338)
Net cash provided by investing activities	25,058	17,720
Financing activities
Proceeds from exercise of stock options	565	413
Net cash provided by financing activities	565	413
Net increase (decrease) in cash, cash equivalents and restricted cash	26,669	(6,487)
Cash, cash equivalents and restricted cash, beginning of period	13,021	16,690
Cash, cash equivalents and restricted cash, end of period	$ 39,690	$ 10,203