Note 1 - Summary of Significant Accounting Policies - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Balance	$ 144	$ 175	$ 200
Bad Debt Expense (Benefit)	46	75	80
Write-offs	70	106	105
Balance	$ 120	$ 144	$ 175