CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net loss	$ (62,970)	$ (66,135)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,862	1,749
Amortization of investment discount	(400)	(413)
Equity-based compensation	9,409	12,476
Amortization of debt discount and issuance costs	7,370	4,529
Loss on disposal of property and equipment	577	540
(Increase) decrease in assets:
Accounts receivable	(782)	506
Inventory	(3,286)	(5,206)
Prepaid expense and other	(319)	(212)
Increase (decrease) in liabilities:
Accounts payable	788	(524)
Accrued liabilities, and other	(2,115)	(18)
Accrued interest	(1,071)	191
Deferred revenue and income	33	(918)
Deferred compensation	(25)	5
Net cash used in operating activities	(50,929)	(53,430)
Cash flows from investing activities:
Purchases of equipment	(148)	(842)
Purchase of marketable securities	(20,710)	(115,634)
Proceeds from sales of marketable securities	13,400	3,000
Maturities of marketable securities	78,922	74,496
Net cash provided by (used in) investing activities	71,464	(38,980)
Cash flows from financing activities:
Proceeds from issuance of common stock	1,363	447
Proceeds from exercise of options	4,879	3,710
Proceeds from issuance of convertible note	0	171,500
Prepayment of forward stock repurchase transaction	0	(45,069)
Payment of debt issuance costs	0	(4,992)
Net cash provided by financing activities	6,242	125,596
Effect of exchange rate on cash	(99)	(77)
Increase in cash and cash equivalents	26,678	33,109
Cash and cash equivalents, beginning of period	66,260	28,513
Cash and cash equivalents, end of period	92,938	61,622
Non-cash investing activities:
Transfer of instruments from inventory to property and equipment	3,225	4,061
Supplemental cash flow information:
Interest paid	4,288	2,001
Income taxes paid	$ 54	$ 435