Note 6 - Concentration or Revenue - Concentration of Revenue (Details) - Customer Concentration Risk [Member] - Sales Revenue, Net [Member]	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Customer A [Member]
Concentration risk	6.10%	14.70%	8.10%	19.00%
Customer B [Member]
Concentration risk	8.90%	3.00%	10.60%	2.50%
Customer C [Member]
Concentration risk	9.10%	15.50%	11.30%	12.40%
Customer D [Member]
Concentration risk	46.60%	14.90%	35.10%	14.80%
Customer E [Member]
Concentration risk	5.80%	10.60%	7.00%	9.50%