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Property, Plant, Equipment and Mine Development
3 Months Ended
Mar. 31, 2020
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 March 31, 2020 and December 31, 2019 is set forth in the table below:
 
March 31, 2020
 
December 31, 2019
 
(Dollars in millions)
Land and coal interests
$
4,025.4

 
$
4,022.4

Buildings and improvements
557.6

 
547.9

Machinery and equipment
1,534.4

 
1,518.6

Less: Accumulated depreciation, depletion and amortization
(1,509.6
)
 
(1,409.8
)
Property, plant, equipment and mine development, net
$
4,607.8

 
$
4,679.1