Note 2 - Summary of Significant Accounting Policies - Allowance for Doubtful Accounts (Details) - SEC Schedule, 12-09, Allowance, Credit Loss [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts, beginning of year	$ 17	$ 5	$ 21
Charge (credit) to costs and expenses	131	13	(16)
Deductions	(101)	(1)
Allowance for doubtful accounts, end of year	$ 47	$ 17	$ 5