Note 3 - Revenue - Total Revenue by Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue	$ 30,418	$ 30,548	$ 55,141	$ 51,812
Percentage of Revenue	100.00%	100.00%	100.00%	100.00%
UNITED STATES
Revenue	$ 22,937	$ 24,773	$ 43,026	$ 41,682
Percentage of Revenue	76.00%	81.00%	78.00%	81.00%
Europe [Member]
Revenue	$ 4,927	$ 3,498	$ 7,454	$ 5,889
Percentage of Revenue	16.00%	11.00%	14.00%	11.00%
Other Location [Member]
Revenue	$ 2,554	$ 2,277	$ 4,661	$ 4,241
Percentage of Revenue	8.00%	8.00%	8.00%	8.00%