Note 2 - Revenue Recognition - Components of Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Trade receivables	$ 2,122	$ 5,015
Unbilled receivables	1,277	2,348
Other short-term receivables	83	20
Allowance for doubtful accounts	(223)	(835)	$ (1,816)
Total accounts receivable	$ 3,259	$ 6,548