Note 12 - Property and Equipment, Net - Property, Plant, and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Property and equipment, gross	$ 1,513,538	$ 1,490,218	$ 1,481,468
Less: accumulated depreciation and depletion	996,395	963,202	941,415
Property and equipment, net	517,143	527,016	540,053
Equipment and Vehicles [Member]
Property and equipment, gross	991,812	950,416	959,083
Mining Properties and Mineral Rights [Member]
Property and equipment, gross	195,284	206,073	196,033
Land and Land Improvements [Member]
Property and equipment, gross	127,417	135,639	135,707
Building and Building Improvements [Member]
Property and equipment, gross	122,343	124,578	121,387
Furniture and Fixtures [Member]
Property and equipment, gross	$ 76,682	$ 73,512	$ 69,258

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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