Note 10 - Segment Reporting - Revenue by Country (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues from external customers	$ 24,744	$ 21,796	$ 69,837	$ 62,141
Revenues, percent	100.00%	100.00%	100.00%	100.00%
UNITED STATES
Revenues from external customers	$ 15,359	$ 13,631	$ 44,436	$ 38,209
Revenues, percent	62.00%	62.00%	64.00%	61.00%
UNITED KINGDOM
Revenues from external customers	$ 3,811	$ 3,634	$ 9,205	$ 10,434
Revenues, percent	15.00%	17.00%	13.00%	17.00%
All Others [Member]
Revenues from external customers	$ 5,574	$ 4,531	$ 16,196	$ 13,498
Revenues, percent	23.00%	21.00%	23.00%	22.00%