Property, Plant and Equipment, Net
 6 Months Ended
Jun. 30, 2021
Property, Plant and Equipment [Abstract]  
Property, Plant and Equipment, Net Property, Plant and Equipment, Net:
 
Property, plant and equipment, net, consists of the following (in millions):
 June 30,
2021		December 31,
2020
Land, buildings and structures, and leasehold improvements$540.1 $544.5 
Machinery and equipment1,076.1 1,035.4 
Office furniture and equipment55.1 50.7 
Mineral interests174.0 172.4 
Construction in progress43.6 43.7 
 1,888.9 1,846.7 
Less: accumulated depreciation and depletion(1,055.1)(995.0)
Property, plant and equipment, net$833.8 $851.7