Property, Plant and Equipment (Summary of PP&E) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total	$ 550,862	$ 1,995,542
Accumulated depreciation and depletion	(95,783)	(1,587,435)
Property, plant and equipment, net	455,079	408,107
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Total	380,318	1,727,454
Buildings, Improvements And Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total	85,082	171,635
Automobiles, Trucks, Tractors and Trailers [Member]
Property, Plant and Equipment [Line Items]
Total	7,534	11,742
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total	19,996	31,407
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Total	6,122	4,793
Land [Member]
Property, Plant and Equipment [Line Items]
Total	31,782	33,394
Oil and Gas Properties [Member]
Property, Plant and Equipment [Line Items]
Total	$ 20,028	$ 15,117