Note 3 - Balance Sheet Components - Summary of Balance Sheet Amounts (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Cash	$ 21,579	$ 23,977
Cash equivalents	66,535	68,390
Cash and cash equivalents	88,114	92,367
Restricted cash	523	525
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Ending Balance	88,637	92,892
Inventories:
Finished goods	2,945	3,071
Raw materials	930	1,047
Reserve for obsolescence	(169)	(339)
Inventory, Net, Total	3,706	3,779
Other accrued expenses:
Sales returns	195	189
Employee-related expense	960	1,149
Warehousing, inventory-related and other	698	584
Accrued Liabilities, Current, Total	1,853	1,922
Deferred revenue:
Deferred revenue	5,713	3,091
Unshipped Product [Member]
Deferred revenue:
Deferred revenue	3,686	1,005
Auto ship advances [Member]
Deferred revenue:
Deferred revenue	1,918	1,977
Product and Service, Other [Member]
Deferred revenue:
Deferred revenue	$ 109	$ 109