Note 10 - Segment Information - Geographic Data (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net revenues	$ 58,388	$ 48,752	$ 172,191	$ 131,361
BRAZIL
Net revenues	$ 12,644	$ 11,132	$ 39,100	$ 29,232
BRAZIL | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
Percent of consolidated net revenue	21.70%	22.80%	22.70%	22.30%
SOUTH AFRICA
Net revenues	$ 6,807	$ 6,703	$ 21,651	$ 19,646
SOUTH AFRICA | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
Percent of consolidated net revenue	11.70%	13.70%	12.60%	15.00%
MEXICO
Net revenues	$ 5,142	$ 6,115	$ 15,738	$ 16,177
MEXICO | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
Percent of consolidated net revenue	8.80%	12.50%	9.10%	12.30%
CHINA
Net revenues	$ 3,338	$ 2,868	$ 9,870	$ 7,396
CHINA | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
Percent of consolidated net revenue	5.70%	5.90%	5.70%	5.60%
JAPAN
Net revenues	$ 3,080	$ 2,426	$ 8,086	$ 5,970
JAPAN | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
Percent of consolidated net revenue	5.30%	5.00%	4.70%	4.50%
INDIA
Net revenues	$ 2,065	$ 1,947	$ 6,871	$ 5,397
INDIA | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
Percent of consolidated net revenue	3.50%	4.00%	4.00%	4.10%
CANADA
Net revenues	$ 1,947	$ 1,499	$ 5,725	$ 4,544
CANADA | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
Percent of consolidated net revenue	3.30%	3.10%	3.30%	3.50%
AUSTRALIA
Net revenues	$ 892	$ 935	$ 2,629	$ 2,741
AUSTRALIA | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
Percent of consolidated net revenue	1.50%	1.90%	1.50%	2.10%
TURKEY
Net revenues	$ 60	$ 65	$ 183	$ 189
TURKEY | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
Percent of consolidated net revenue	0.10%	0.10%	0.10%	0.10%
International [Member]
Net revenues	$ 35,975	$ 33,690	$ 109,853	$ 91,292
International [Member] | Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
Percent of consolidated net revenue	61.60%	69.00%	63.70%	69.50%