Note 3 - Revenue 1 (Details Textual) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Number Of Units Installed	1,100		1,100
Unbilled Receivables, Current	$ 1,929		$ 1,929		$ 1,857
Contract with Customer, Liability, Current	357		357		$ 712
Contract with Customer, Liability, Revenue Recognized	$ 97	$ 302	$ 555	$ 1,059
Contract with Customer, Contracts in Progress, Number of Contracts Identified as Loss Contracts	3		3		3
Provision for Loss on Contracts	$ 3		$ 3		$ 26
Revenue, Remaining Performance Obligation, Amount	$ 6,417		$ 6,417
Minimum [Member]
Contract Term (Month)			180 days
Maximum [Member]
Contract Term (Month)			1 year 180 days