Note 3 - Reserve for Sales Returns and Allownace - Reserve for Sales Returns and Allowances (Details) - Allowance for Sales Returns [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance at the beginning of year	$ 1,967	$ 1,384	$ 1,308
Provision for returns and allowances	2,789	4,445	4,547
Actual returns and allowances paid to customers	(3,631)	(3,862)	(4,471)
Balance at the end of year	$ 1,125	$ 1,967	$ 1,384