Note 4 - Accounts Receivable - Summary of Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts receivable, gross	$ 35,408	$ 35,264
Less: allowance for doubtful accounts	(3,936)	(2,729)	$ (1,115)
Accounts receivable, net	31,472	32,535
Retail Customers [Member]
Accounts receivable, gross	21,732	22,227
Wholesale Carriers [Member]
Accounts receivable, gross	9,315	8,146
Other [Member]
Accounts receivable, gross	$ 4,361	$ 4,891

Amounts due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer) for goods or services (including trade receivables) that have been delivered or sold in the normal course of business.

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+ References

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