Note 4 - Accounts Receivable - Summary of Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Balance, beginning	$ 3,936	$ 2,729
Provision for uncollectible accounts	257	2,745
Charged to other accounts	1,253	(921)
Deductions	(819)	(617)
Balance, ending	$ 4,627	$ 3,936