Note 16 - Geographical Information (Details Textual)	3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Number of Products Sold by Entity	1
Number of Industries in Which Products are Sold	1
Number of Reportable Segments	1
Revenue from Contract with Customer, Including Assessed Tax	$ 1,817,000	$ 3,746,000
Customer Concentration Risk [Member] | Revenue Benchmark [Member]
Number of Major Customers	2	2
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Two Major Customers [Member]
Revenue from Contract with Customer, Including Assessed Tax	$ 822,000	$ 2,176
Customer Concentration Risk [Member] | Accounts Receivable [Member]
Number of Major Customers	2		1
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Two Major Customers [Member]
Accounts Receivable, before Allowance for Credit Loss, Current	$ 2,158
Customer Concentration Risk [Member] | Accounts Receivable [Member] | One Major Customer [Member]
Accounts Receivable, before Allowance for Credit Loss, Current			$ 2,051,000