XML 61 R48.htm IDEA: XBRL DOCUMENT v3.25.1
Property, Plant, Equipment and Mine Development (Details) - USD ($)
$ in Millions
Mar. 31, 2025
Dec. 31, 2024
Property, Plant and Equipment [Line Items]    
Less: Accumulated depreciation, depletion and amortization $ (2,456.8) $ (2,372.5)
Property, plant, equipment and mine development, net 3,058.0 3,081.5
Land and coal interests    
Property, Plant and Equipment [Line Items]    
Property, Plant, Equipment, and mine development, gross 2,647.5 2,648.5
Buildings and improvements    
Property, Plant and Equipment [Line Items]    
Property, Plant, Equipment, and mine development, gross 738.5 726.7
Machinery and equipment    
Property, Plant and Equipment [Line Items]    
Property, Plant, Equipment, and mine development, gross $ 2,128.8 $ 2,078.8