Note 5 - Revenues - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Allowance for doubtful accounts, Balance	$ 271	$ 267	$ 275	$ 255
Provision for losses on accounts receivable	9	9	23	27
Write-offs less recoverieis	(4)	(3)	(22)	(9)
Allowance for doubtful accounts, Balance	$ 276	$ 273	$ 276	$ 273