Property, Plant and Equipment, Net
9 Months Ended
Sep. 30, 2012
Property, Plant and Equipment, Net [Abstract]  
Property, Plant and Equipment, Net
4.  Property, Plant and Equipment, Net:
 
Property, plant and equipment, net consists of the following (in millions):

   
September 30,
  
December 31,
 
   
2012
  
2011
 
Land, buildings and structures and leasehold improvements
 $288.2  $275.9 
Machinery and equipment
  571.8   541.8 
Office furniture and equipment
  21.9   21.3 
Mineral interests
  178.5   174.4 
Construction in progress
  148.1   68.8 
    1,208.5   1,082.2 
Less accumulated depreciation and depletion
  (568.2)  (508.8)
Property, plant and equipment, net
 $640.3  $573.4