CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Statement of Cash Flows [Abstract]
Net loss	$ (6,641)	$ (9,903)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	439	316
Provision for inventory obsolescence	413	36
Stock based compensation	2,146	2,051
Unrealized gain on short term investments	0	(164)
Provision (benefit) for allowance for doubtful accounts	486	(238)
Changes in operating assets and liabilities:
Trade receivables	1,195	(1,333)
Prepaid expenses and other assets	(7,427)	(879)
Inventories	(571)	(1,015)
Accounts payable	(232)	218
Accrued and other liabilities	(2,241)	236
Net cash used in operating activities	(12,433)	(10,675)
Cash flows from investing activities
Purchases of property and equipment	(184)	(518)
Purchases of marketable securities	0	(18,884)
Proceeds from maturities of marketable securities	0	80,726
Net cash (used in) provided by investing activities	(184)	61,324
Cash flows from financing activities
Proceeds from stock option exercises	72	115
Repayment of finance lease liabilities	(120)	0
Net cash (used in) provided by financing activities	(48)	115
Effect of exchange rates on cash	9	0
Net change in cash, cash equivalents and restricted cash	(12,656)	50,764
Cash, cash equivalents and restricted cash, beginning of period	58,812	16,596
Cash, cash equivalents and restricted cash, end of period	46,156	67,360
Supplemental Cash Flow Information [Abstract]
Interest	8	14
Taxes	54	248
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Cashless exercise of stock options	49	757
Right-of-use assets capitalized and lease liabilities recognized upon adoption of Topic 842	0	212
Right-of-use assets capitalized and lease liabilities recognized upon lease remeasurement	0	207
Right-of-use assets capitalized and lease liabilities recognized upon execution of lease	150	0
Transfer of other assets to fixed assets	0	42
Transfer of inventory (to) from fixed assets	$ (34)	$ 262