Note 10 - Concentration of Credit Risk (Details Textual) - Customer Concentration Risk [Member]	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Revenue Benchmark [Member]
Number of Major Customers	2	2	2	2
Revenue Benchmark [Member] | Customer One [Member]
Concentration Risk, Percentage	22.00%	24.00%	27.00%	27.00%
Revenue Benchmark [Member] | Customer Two [Member]
Concentration Risk, Percentage	19.00%	27.00%	28.00%	30.00%
Accounts Receivable [Member] | Customer One [Member]
Accounts Receivable, before Allowance for Credit Loss	$ 1,777,000	$ 2,241,000	$ 1,777,000	$ 2,241,000
Concentration Risk, Percentage			26.00%	22.00%
Accounts Receivable [Member] | Customer Two [Member]
Accounts Receivable, before Allowance for Credit Loss	$ 996,000	$ 1,702,000	$ 996,000	$ 1,702,000
Concentration Risk, Percentage			14.00%	17.00%