Note 9 - Segment Information - Geographic Data (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net revenues	$ 54,579	$ 39,886
BRAZIL
Net revenues	$ 13,410	$ 9,943
BRAZIL | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
% of consolidated net revenue	24.60%	24.90%
SOUTH AFRICA
Net revenues	$ 7,444	$ 6,027
SOUTH AFRICA | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
% of consolidated net revenue	13.60%	15.10%
MEXICO
Net revenues	$ 5,360	$ 4,688
MEXICO | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
% of consolidated net revenue	9.80%	11.80%
CHINA
Net revenues	$ 2,442	$ 2,408
CHINA | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
% of consolidated net revenue	4.50%	6.00%
INDIA
Net revenues	$ 2,424	$ 1,612
INDIA | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
% of consolidated net revenue	4.40%	4.00%
JAPAN
Net revenues	$ 2,247	$ 1,709
JAPAN | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
% of consolidated net revenue	4.10%	4.30%
CANADA
Net revenues	$ 1,934	$ 1,303
CANADA | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
% of consolidated net revenue	3.50%	3.30%
AUSTRALIA
Net revenues	$ 886	$ 810
AUSTRALIA | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
% of consolidated net revenue	1.60%	2.00%
TURKEY
Net revenues	$ 63	$ 65
TURKEY | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
% of consolidated net revenue	0.10%	0.20%
International [Member]
Net revenues	$ 36,210	$ 28,565
International [Member] | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
% of consolidated net revenue	66.20%	71.60%