Note 5 - Operating Assets and Liabilities - Summary of Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Trade receivables	$ 33,467	$ 30,173
Other receivables	6,186	1,819
Less: Allowance for doubtful accounts	(1,201)	(2,045)
Total accounts receivable, net	$ 38,452	$ 29,947