Note 3 - Property, Plant and Equipment - Depreciation and amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment.
Depreciation of plant and equipment	$ 30,913	$ 24,132	$ 17,945
Amortization of right of use assets (finance leases)	8,547	4,846	1,109
Amortization and depletion of capitalized mine development costs and mineral rights	14,792	12,216	7,151
Total depreciation, depletion, and amortization	$ 54,252	$ 41,194	$ 26,205