Note 1 - Summary of Significant Accounting Policies - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Balance	$ 120	$ 144	$ 175
Bad debt expense	38	46	75
Write-offs, net of recoveries	64	70	106
Balance	$ 94	$ 120	$ 144