Note 1 - Description of Business and Summary of Significant Accounting Policies - Trade Revenue and Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Trade revenue	$ 8	$ 3	$ 2
Trade expense	(8)	(3)	(2)
Net trade (loss) income	$ 0	$ 0	$ 0