Note 9 - Details of Selected Balance Sheet Accounts - Multi-client Library Costs and Accumulated Amortization (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Gross costs of multi-client data creation	$ 1,024,429	$ 1,021,758
Less: accumulated amortization	(841,985)	(838,700)
Less: impairments to multi-client data library	(132,144)	(132,144)
Multi-client data library, net	$ 50,300	$ 50,914