Inventories (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Inventory Disclosure [Abstract]    
Raw materials $ 80.5 $ 114.6
Work in process 466.8 505.1
Finished goods 908.1 1,025.5
Operating materials and supplies 67.6 73.1
Total Inventory $ 1,523.0 $ 1,718.3