Note 3 - Trade Accounts Receivable - Accounts Receivable Balances (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Billed	$ 105,992	$ 68,584
Unbilled	20,388	12,629
Current estimated credit losses	(4,526)	(3,482)	$ (2,952)	$ (2,224)
Total accounts receivable—net	$ 121,854	$ 77,731

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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Amount of allowance for credit loss on accounts receivable, classified as current.

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