Consolidated Statement of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net loss	$ (84,305)	$ (88,326)	$ (64,028)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,602	2,561	2,196
Amortization of investment discount	(427)	(621)	326
Equity-based compensation expense	12,618	14,422	13,933
Amortization of debt discount and issuance costs	9,969	6,849	0
Loss on disposal of property and equipment	837	678	240
(Increase) decrease in assets:
Accounts receivable	(1,362)	86	(1,912)
Inventory	(3,655)	(4,223)	(7,759)
Prepaid expense and other assets	(752)	(250)	(459)
Increase (decrease) in liabilities:
Accounts payable	988	(748)	1,064
Accrued liabilities	(1,327)	1,426	596
Accrued interest	0	1,262	0
Deferred revenue and income	54	(904)	36
Deferred compensation	(34)	32	21
Net cash used in operating activities	(64,794)	(67,756)	(55,746)
Cash flows from investing activities:
Purchases of equipment	(330)	(998)	(2,966)
Purchase of marketable securities	(50,226)	(120,556)	(82,333)
Proceeds from sales of marketable securities	14,500	3,000	11,522
Maturities of marketable securities	88,867	98,416	48,049
Net cash provided by (used in) investing activities	52,811	(20,138)	(25,728)
Cash flows from financing activities:
Proceeds from issuance of common stock	1,458	583	83,821
Proceeds from exercise of options and warrants	5,365	3,749	6,606
Proceeds from issuance of convertible note	0	171,500	0
Prepayment of forward stock repurchase transaction	0	(45,069)	0
Payment of debt issuance costs	0	(4,992)	0
Net cash provided by financing activities	6,823	125,771	90,427
Effect of exchange rate on cash	(86)	(130)	316
Increase (decrease) in cash and cash equivalents	(5,246)	37,747	9,269
Cash and cash equivalents, beginning of period	66,260	28,513	19,244
Cash and cash equivalents, end of period	61,014	66,260	28,513
Non-cash investing activities:
Transfer of instruments from inventory to property and equipment	3,361	4,767	0
Supplemental Cash Flow Information [Abstract]
Interest paid	4,288	2,001	0
Income taxes paid, net of refunds	$ 41	$ 651	$ 0