Note 7 - Concentration or Revenue - Concentration of Revenue (Details) - Customer Concentration Risk [Member] - Sales Revenue, Net [Member]	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Customer A [Member]
Concentration risk	15.40%	10.50%	10.10%	15.20%
Customer B [Member]
Concentration risk	14.30%	7.30%	11.60%	4.60%
Customer C [Member]
Concentration risk	13.10%	8.00%	11.80%	10.40%
Customer D [Member]
Concentration risk	7.30%	43.40%	27.40%	27.80%