Note 3 - Balance Sheet Components - Summary of Balance Sheet Amounts (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Cash, cash equivalents and restricted cash:
Cash	$ 14,020	$ 13,720
Cash equivalents	79,186	82,315
Cash and cash equivalents	93,206	96,035
Restricted cash	513	3,390
Cash, cash equivalents and restricted cash	93,719	99,425	$ 111,106	$ 135,651
Inventories:
Finished goods	3,368	6,142
Raw materials	1,253	1,249
Reserve for obsolescence	(507)	(987)
Inventories	4,114	6,404
Other accrued expenses:
Sales returns	195	373
Employee-related expense	994	1,258
Warehousing, inventory-related and other	574	756
Other accrued expenses	1,763	2,387
Deferred revenue:
Deferred revenue	2,645	4,506
Unshipped Product [Member]
Deferred revenue:
Deferred revenue	584	2,390
Auto ship advances [Member]
Deferred revenue:
Deferred revenue	1,955	1,985
Product and Service, Other [Member]
Deferred revenue:
Deferred revenue	$ 106	$ 131