CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net loss	$ (9,665)	$ (8,137)	$ (17,286)
Adjustments to reconcile net loss to net cash used for operating activities:
Depreciation and amortization	1,744	1,426	1,612
Stock compensation expense	13,179	7,223	2,680
Change in fair value of warrants	0	2,524	257
Loss on extinguishment of debt	0	838	860
Foreign currency translation loss	42	51	37
Gain (loss) on sale of fixed assets	0	22	(115)
Amortization of premiums and discounts on marketable securities	(610)	(327)	0
Non-cash lease cost	2,787	0	0
Changes in operating assets and liabilities:
Inventory	(3,258)	235	(305)
Accounts receivable	(8,714)	(5,184)	(1,177)
Prepaid and other current assets	(106)	(1,267)	(261)
Accounts payable	(1,024)	899	(1,361)
Accrued expenses	1,018	1,493	1,050
Operating lease liabilities	(2,512)
Other non-current assets and liabilities, net	(64)	(208)	826
Net cash used for operating activities	(7,183)	(412)	(13,183)
Investing activities:
Purchases of short term investments	(63,092)	(66,549)	0
Maturities of short term investments	85,577	2,200	0
Purchases of long term investments	(9,254)	0	0
Expenditures for property, plant and equipment	(2,616)	(2,678)	(1,510)
Net cash provided by (used for) investing activities	10,615	(67,027)	(1,510)
Financing activities:
Net proceeds from equity offering	0	70,028	0
Net proceeds from common stock issuance due to stock option exercises	5,286	4,361	8,220
Deferred financing costs	0	0	(30)
Proceeds from exercise of warrants	0	2,716	4,010
Borrowings under revolving and term loan credit agreements	0	0	14,793
Warrants issued in connection with debt arrangement	0	0	207
Payments on term loan credit agreement	0	0	(889)
Payments on long-term debt	0	(17,532)	(7,151)
Fee on long-term debt	0	(710)	(583)
Other	(26)	0	0
Net cash provided by financing activities	5,260	58,863	18,577
Net increase (decrease) in cash, cash equivalents, and restricted cash	8,692	(8,576)	3,884
Cash, cash equivalents, and restricted cash at beginning of period	18,286	26,862	22,978
Cash, cash equivalents, and restricted cash at end of period	$ 26,978	$ 18,286	$ 26,862