Note 3 - Concentrations - Concentration Risk, by Risk Factor (Details) - Customer Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts Receivable [Member] | Customer A [Member]
Concentration risk, percentage	15.00%	13.00%
Accounts Receivable [Member] | Customer B [Member]
Concentration risk, percentage	13.00%	13.00%
Accounts Receivable [Member] | Customer D [Member]
Concentration risk, percentage	19.00%
Revenue from Contract with Customer Benchmark [Member] | Customer A [Member]
Concentration risk, percentage	14.00%	18.00%	12.00%
Revenue from Contract with Customer Benchmark [Member] | Customer B [Member]
Concentration risk, percentage			12.00%
Revenue from Contract with Customer Benchmark [Member] | Customer C [Member]
Concentration risk, percentage	11.00%
Revenue from Contract with Customer Benchmark [Member] | Customer E [Member]
Concentration risk, percentage		11.00%