Note 5 - Accounts Receivable - Summary of Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accounts receivable, gross	$ 29,834	$ 35,408
Less: allowance for doubtful accounts	(4,175)	(3,936)
Accounts receivable, net	25,659	31,472
Retail Customers [Member]
Accounts receivable, gross	19,537	21,732
Wholesale Carriers [Member]
Accounts receivable, gross	6,145	9,315
Other [Member]
Accounts receivable, gross	$ 4,152	$ 4,361