Note 1 - Description of Business and Summary of Significant Accounting Policies - Trade Revenue and Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Trade revenue	$ 2,897	$ 1,832	$ 2,069
Trade expense	(3,012)	(1,863)	(1,997)
Net trade (loss) income	$ (115)	$ (31)	$ 72