Note 12 - Property and Equipment, Net - Property, Plant, and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Property and equipment, gross	$ 1,506,245	$ 1,490,218	$ 1,457,754
Less: accumulated depreciation and depletion	978,072	963,202	922,796
Property and equipment, net	528,173	527,016	534,958
Equipment and Vehicles [Member]
Property and equipment, gross	967,636	950,416	942,116
Mining Properties and Mineral Rights [Member]
Property and equipment, gross	202,620	206,073	188,380
Land and Land Improvements [Member]
Property and equipment, gross	134,837	135,639	134,147
Building and Building Improvements [Member]
Property and equipment, gross	125,944	124,578	124,784
Furniture and Fixtures [Member]
Property and equipment, gross	$ 75,208	$ 73,512	$ 68,327

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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