Note 5 - Accounts Receivable and Customer Concentrations - Concentration of Revenue (Details) - Customer Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Customer A [Member] | Sales Revenue, Net [Member]
Concentration risk	4.90%	9.30%
Customer A [Member] | Accounts Receivable [Member]
Concentration risk	4.80%	15.20%
Customer B [Member] | Sales Revenue, Net [Member]
Concentration risk	13.20%	26.60%
Customer B [Member] | Accounts Receivable [Member]
Concentration risk	13.90%	25.80%
Customer C [Member] | Sales Revenue, Net [Member]
Concentration risk	7.20%	11.90%
Customer C [Member] | Accounts Receivable [Member]
Concentration risk	4.00%	9.00%
Customer D [Member] | Sales Revenue, Net [Member]
Concentration risk	3.80%	11.30%
Customer D [Member] | Accounts Receivable [Member]
Concentration risk	0.10%	7.60%
Customer E [Member]
Concentration risk	40.10%
Customer E [Member] | Sales Revenue, Net [Member]
Concentration risk	52.60%
Customer E [Member] | Accounts Receivable [Member]
Concentration risk