CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net loss	$ (21,309,000)	$ (21,721,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	755,000	626,000
Amortization of investment discount	(4,000)	(180,000)
Equity-based compensation	4,199,000	3,397,000
Provision for bad debt expense	8,000	0
Amortization of debt discount and issuance costs	2,674,000	2,387,000
Unrealized loss on equity investments	8,000	0
Realized loss (gain) on sale of investments	3,000	(2,000)
Loss on disposal of property and equipment	432,000	329,000
(Increase) decrease in assets:
Accounts receivable	(9,000)	(90,000)
Inventory	(1,735,000)	(1,567,000)
Prepaid expense and other	(1,030,000)	(1,041,000)
Increase (decrease) in liabilities:
Accounts payable	968,000	1,151,000
Accrued liabilities, and other	(1,475,000)	(1,790,000)
Accrued interest	(1,071,000)	(1,071,000)
Deferred revenue and income	(85,000)	74,000
Deferred compensation	74,000	(7,000)
Net cash used in operating activities	(17,597,000)	(19,505,000)
Cash flows from investing activities:
Purchases of equipment	(438,000)	(37,000)
Purchase of marketable securities	(21,582,000)	(12,826,000)
Proceeds from sales of marketable securities	0	9,000,000
Maturities of marketable securities	16,664,000	28,662,000
Net cash (used in) provided by investing activities	(5,356,000)	24,799,000
Cash flows from financing activities:
Proceeds from issuance of common stock	111,000	139,000
Proceeds from exercise of options	1,318,000	3,677,000
Net cash provided by financing activities	1,429,000	3,816,000
Effect of exchange rate on cash	(3,000)	(61,000)
(Decrease) increase in cash and cash equivalents	(21,527,000)	9,049,000
Cash and cash equivalents, beginning of period	61,014,000	66,260,000
Cash and cash equivalents, end of period	39,487,000	75,309,000
Non-cash investing activities:
Transfer of instruments from inventory to property and equipment	1,282,000	769,000
Supplemental cash flow information:
Interest paid	2,144,000	2,144,000
Income taxes paid, net of refunds	$ 26,000	$ 2,000