Note 5 - Accounts Receivable - Summary of Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accounts receivable, gross	$ 27,124	$ 35,408
Less: allowance for doubtful accounts	(4,653)	(3,936)
Accounts receivable, net	22,471	31,472
Retail Customers [Member]
Accounts receivable, gross	16,838	21,732
Wholesale Carriers [Member]
Accounts receivable, gross	5,831	9,315
Other [Member]
Accounts receivable, gross	$ 4,455	$ 4,361