Note 3 - Revenue 1 (Details Textual) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Number Of Units Installed	1,200
Contract with Customer, Asset, after Allowance for Credit Loss, Total	$ 355		$ 1,927
Contract with Customer, Liability, Current	787		$ 850
Contract with Customer, Liability, Revenue Recognized	$ 108	$ 248
Contract with Customer, Contracts in Progress, Number of Contracts Identified as Loss Contracts	1		1
Provision for Loss on Contracts	$ 50		$ 176
Revenue, Remaining Performance Obligation, Amount	$ 5,151
Minimum [Member]
Contract Term (Month)	180 days
Maximum [Member]
Contract Term (Month)	1 year 180 days