Note 5 - Environmental and Reclamation Activities - Accrued Reclamation and Closure Cost Liability Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Balance	$ 116,048	$ 108,374	$ 108,389
Accruals for estimated costs	4,952		472
Accretion expense	6,454	5,912	7,122
Revision of estimated cash flows due to changes in reclamation plans	(8,781)	2,543	(4,522)
Payment of reclamation obligations	(5,442)	(781)	(3,087)
Balance	$ 113,231	$ 116,048	$ 108,374