Note 3 - Accounts Receivable and Accounts Receivable Allowance - Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts receivable	$ 218,832	$ 220,455
Allowance	(14,037)	(13,683)	$ (14,799)
Accounts receivable, net	$ 204,795	$ 206,772

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

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