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, 2018	Dec. 31, 2017	Dec. 31, 2016
Balance at the beginning of year	$ 1,125	$ 1,967	$ 1,384
Provision for returns and allowances	4,908	2,789	4,445
Actual returns and allowances paid to customers	(4,140)	(3,631)	(3,862)
Balance at the end of year	$ 1,893	$ 1,125	$ 1,967