Note 12 - Property and Equipment, Net - Property, Plant, and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Property and equipment, gross	$ 1,513,794	$ 1,490,218	$ 1,489,401
Less: accumulated depreciation and depletion	1,003,136	963,202	953,145
Property and equipment, net	510,658	527,016	536,256
Equipment and Vehicles [Member]
Property and equipment, gross	997,560	950,416	959,828
Mining Properties and Mineral Rights [Member]
Property and equipment, gross	188,838	206,073	199,677
Land and Land Improvements [Member]
Property and equipment, gross	126,130	135,639	135,102
Building and Building Improvements [Member]
Property and equipment, gross	123,207	124,578	122,119
Furniture and Fixtures [Member]
Property and equipment, gross	$ 78,059	$ 73,512	$ 72,675

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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