Note 5 - Accounts Receivable - Activity in Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Balance	$ 754	$ 617
Acquired allowance on accounts receivable (Note 3)	0	50
Additions charged to expense	61	339
Reductions to allowance, net	0	(252)
Balance	$ 815	$ 754