Note 5 - Leases (Details Textual) $ in Thousands			1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Oct. 30, 2018 ft²	Oct. 01, 2018 USD ($)	Aug. 31, 2020 USD ($) ft²	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Mar. 31, 2017 ft²
Short-term and Variable Lease, Cost				$ 100	$ 100	$ 200	$ 200
Lease, Cost, Total				$ 400	$ 500	800	1,300
Operating Lease, Payments						$ 1,000	1,400
Operating Lease, Weighted Average Remaining Lease Term (Year)				3 years 4 months 24 days		3 years 4 months 24 days
Operating Lease, Weighted Average Discount Rate, Percent				7.65%		7.65%
Write-off of Lease Receivable and Prepaid Commission Assets						$ 0	$ 1,383
The 1020 Marsh Road Facility [Member]
Area of Real Estate Property (Square Foot) | ft²									34,500
Lessee, Operating Lease, Term of Contract (Month)									87 months
Lessee, Operating Lease, Number of Renewal Options									1
Lessee, Operating Lease, Renewal Term (Year)									5 years
The 1020 Marsh Road Facility [Member] | EVA Automation, Inc. [Member]
Lessor, Operating Lease, Term of Contract (Month)		72 months
Incentive to Lessee		$ 900
Lessor, Operating Lease, Abatement Term (Month)		5 months
Write-off of Lease Receivable and Prepaid Commission Assets						1,400
Operating Lease, Lease Income (Loss)						(700)		$ (13)
Proceeds from Lease Payment, Operating Activity						$ 400		$ 1,200
Sublease Agreement in Palo Alto, California [Member]
Area of Real Estate Property (Square Foot) | ft²	4,240
Lease Expiration Date	Aug. 31, 2020
Office Space in North Carolina [Member]
Area of Real Estate Property (Square Foot) | ft²			4,128
Lessee, Operating Lease, Term of Contract (Month)			63 months
Lessee, Operating Lease, Monthly Payments			$ 9
Lessee, Operating Lease, Abatement Term (Month)			3 months