CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (42,536)	$ (44,037)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,236	1,082
Amortization of investment discount	(320)	(146)
Equity-based compensation	6,278	9,011
Amortization of debt discount and issuance costs	4,843	2,273
Loss on disposal of property and equipment	407	266
(Increase) decrease in assets:
Accounts receivable	(51)	123
Inventory	(2,217)	(4,334)
Prepaid expense and other	(588)	(697)
Increase (decrease) in liabilities:
Accounts payable	476	206
Accrued liabilities, and other	(1,110)	661
Accrued interest	0	1,105
Deferred revenue and income	38	(935)
Deferred compensation	(18)	5
Net cash used in operating activities	(33,562)	(35,417)
Cash flows from investing activities:
Purchases of equipment	(76)	(702)
Purchase of marketable securities	(17,601)	(91,272)
Proceeds from sales of marketable securities	13,400	3,000
Maturities of marketable securities	54,447	38,272
Net cash provided by (used in) investing activities	50,170	(50,702)
Cash flows from financing activities:
Proceeds from issuance of common stock	251	276
Proceeds from exercise of options	4,369	2,757
Proceeds from issuance of convertible note	0	171,499
Prepayment of forward stock repurchase transaction	0	(45,069)
Payment of debt issuance costs	0	(4,991)
Net cash provided by financing activities	4,620	124,472
Effect of exchange rate on cash	(19)	(56)
Increase in cash and cash equivalents	21,209	38,297
Cash and cash equivalents, beginning of period	66,260	28,513
Cash and cash equivalents, end of period	87,469	66,810
Non-cash investing activities:
Transfer of instruments from inventory to property and equipment	1,715	1,196
Supplemental cash flow information:
Interest paid	2,144	0
Income taxes paid	$ 9	$ 39