CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Cash Flows [Abstract]
Net loss	$ (1,951)	$ (5,608)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	214	194
Provision for inventory obsolescence	10	41
Stock based compensation	1,049	1,195
Unrealized gain on short term investments	0	(164)
Provision (benefit) for allowance for doubtful accounts	324	(238)
Changes in operating assets and liabilities:
Trade receivables	1,520	(85)
Prepaid expenses and other assets	(6,024)	(349)
Inventories	(855)	(170)
Accounts payable	107	81
Accrued and other liabilities	(1,801)	14
Net cash used in operating activities	(7,407)	(5,089)
Cash flows from investing activities
Purchases of property and equipment	(90)	(117)
Purchases of marketable securities	0	(18,884)
Proceeds from maturities of marketable securities	0	39,842
Net cash (used in) provided by investing activities	(90)	20,841
Cash flows from financing activities
Proceeds from stock option exercises	72	67
Repayment of finance lease liabilities	(57)	0
Net cash provided by financing activities	15	67
Effect of exchange rates on cash	50	0
Net change in cash, cash equivalents and restricted cash	(7,432)	15,819
Cash, cash equivalents and restricted cash, beginning of period	58,812	16,596
Cash, cash equivalents and restricted cash, end of period	51,380	32,415
Cash paid for:
Interest	6	0
Non cash financing activities:
Cashless exercise of stock options/warrants	11	710
Lease adoption	$ 0	$ 212