Note 15 - Revenue by Product, by Significant Customer and by Geographic Region; Geographic Information - Total Revenue by Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Total Revenue	$ 29,388	$ 27,184	$ 33,462	$ 23,386	$ 28,726	$ 25,789	$ 26,581	$ 22,283	$ 113,420	$ 103,379	$ 92,999
Percentage of Revenue									100.00%	100.00%	100.00%
UNITED STATES
Total Revenue									$ 92,905	$ 83,972	$ 76,621
Percentage of Revenue									82.00%	81.00%	82.00%
Europe [Member]
Total Revenue									$ 12,435	$ 10,953	$ 8,756
Percentage of Revenue									11.00%	11.00%	9.00%
Other Location [Member]
Total Revenue									$ 8,080	$ 8,454	$ 7,622
Percentage of Revenue									7.00%	8.00%	9.00%