Note 3 - Reserve for Sales Returns and Allowance - Reserve for Sales Returns and Allowances (Details) - Allowance For Sales Returns 1 [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Balance at the beginning of year	$ 2,112	$ 1,893	$ 1,125
Provision for returns and allowances	7,699	4,334	4,908
Actual returns and allowances paid to customers	(6,446)	(4,115)	(4,140)
Balance at the end of year	$ 3,365	$ 2,112	$ 1,893