Note 13 - Property and Equipment, Net - Property, Plant, and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Property and equipment, gross	$ 1,449,643	$ 1,403,356	$ 1,405,314
Less: accumulated depreciation and depletion	906,847	853,668	844,696
Property and equipment, net	542,796	549,688	560,618
Equipment and Vehicles [Member]
Property and equipment, gross	949,577	906,275	917,186
Mining Properties and Mineral Rights [Member]
Property and equipment, gross	185,792	180,246	180,004
Land and Land Improvements [Member]
Property and equipment, gross	134,543	142,271	138,875
Building and Building Improvements [Member]
Property and equipment, gross	112,940	108,884	105,895
Furniture and Fixtures [Member]
Property and equipment, gross	$ 66,791	$ 65,680	$ 63,354

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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