v3.26.3
Property, Plant, Equipment and Mine Development
 9 Months Ended
Sep. 30, 2026
Property, Plant, and Equipment [Abstract]  
Property, Plant, Equipment and Mine Development Property, Plant, Equipment and Mine Development
The composition of property, plant, equipment and mine development, net, as of September 30, 2026 and December 31, 2025 is set forth in the table below:
September 30, 2026December 31, 2025
(Dollars in millions)
Land and coal interests$2,689.8 $2,691.2 
Buildings and improvements782.9 758.8 
Machinery and equipment2,473.9 2,377.1 
Less: Accumulated depreciation, depletion and amortization(2,904.4)(2,673.8)
Property, plant, equipment and mine development, net$3,042.2 $3,153.3 
At-Risk Assets
The Company identified certain assets with an aggregate carrying value of approximately $53 million at September 30, 2026 in its Other U.S. Thermal reportable segment whose recoverability is most sensitive to customer concentration risk.