CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net loss	$ (40,539,000)	$ (42,536,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,571,000	1,236,000
Amortization of investment discount	13,000	(320,000)
Equity-based compensation	7,615,000	6,278,000
Amortization of debt discount and issuance costs	5,426,000	4,843,000
Realized loss on sale of investments	3,000	0
Loss on disposal of property and equipment	527,000	407,000
Contributions to deferred compensation plan	(160,000)	0
(Increase) decrease in assets:
Accounts receivable	550,000	(51,000)
Inventory	(1,979,000)	(2,217,000)
Prepaid expense and other	(363,000)	(588,000)
Increase (decrease) in liabilities:
Accounts payable	390,000	476,000
Accrued liabilities, and other	(581,000)	(1,110,000)
Deferred revenue and income	(39,000)	38,000
Deferred compensation	171,000	(18,000)
Net cash used in operating activities	(27,395,000)	(33,562,000)
Cash flows from investing activities:
Purchases of equipment	(643,000)	(76,000)
Purchase of marketable securities	(21,509,000)	(17,601,000)
Proceeds from sales of marketable securities	0	13,400,000
Maturities of marketable securities	27,844,000	54,447,000
Net cash provided by investing activities	5,692,000	50,170,000
Cash flows from financing activities:
Proceeds from issuance of common stock	216,000	251,000
Proceeds from exercise of options	3,031,000	4,369,000
Proceeds from debt	4,791,000	0
Net cash provided by financing activities	8,038,000	4,620,000
Effect of exchange rate on cash	19,000	(19,000)
(Decrease) increase in cash and cash equivalents	(13,646,000)	21,209,000
Cash and cash equivalents, beginning of period	61,014,000	66,260,000
Cash and cash equivalents, end of period	47,368,000	87,469,000
Non-cash investing activities:
Net transfer of instruments from inventory to property and equipment	1,288,000	1,715,000
Supplemental cash flow information:
Interest paid	2,144,000	2,144,000
Income taxes paid, net of refunds	$ 26,000	$ 9,000