Note 3 - Revenue - Total Revenue by Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue	$ 29,697	$ 26,787	$ 84,838	$ 78,599
Percentage of Revenue	100.00%	100.00%	100.00%	100.00%
UNITED STATES
Revenue	$ 23,512	$ 21,695	$ 66,538	$ 63,377
Percentage of Revenue	79.00%	81.00%	78.00%	81.00%
Europe [Member]
Revenue	$ 3,943	$ 3,132	$ 11,396	$ 9,021
Percentage of Revenue	13.00%	12.00%	14.00%	11.00%
Other Location [Member]
Revenue	$ 2,242	$ 1,960	$ 6,904	$ 6,201
Percentage of Revenue	8.00%	7.00%	8.00%	8.00%