Note 2 - Allowance for Doubtful Accounts Receivable - Allowance for Doubtful Accounts Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Balance at the beginning of year	$ 2,964	$ 2,042	$ 1,382
Provision for bad debts - accounts receivable	6,746	1,323	867
Charge-offs	(2,087)	(401)	(210)
Recoveries	44	0	3
Balance at the end of year	$ 7,667	$ 2,964	$ 2,042