Property, Plant and Equipment (Footnote) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Property, Plant and Equipment [Line Items]
Property, plant and equipment classified as assets held for sale	$ 215.9
Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	2 years
Minimum | Land improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	10 years
Minimum | Building and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	10 years
Minimum | Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	2 years
Minimum | Long term mineral rights and production equipment costs
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	7 years
Minimum | Short-lived production equipment components, office and building equipment and other equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	2 years
Minimum | Production process equipment (intermediate components)
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	8 years
Minimum | Production process equipment (major unit components)
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	20 years
Minimum | Production process equipment (infrastructure and other)
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	30 years
Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	60 years
Maximum | Land improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	30 years
Maximum | Building and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	45 years
Maximum | Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	45 years
Maximum | Long term mineral rights and production equipment costs
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	60 years
Maximum | Short-lived production equipment components, office and building equipment and other equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	7 years
Maximum | Production process equipment (intermediate components)
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	19 years
Maximum | Production process equipment (major unit components)
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	29 years
Maximum | Production process equipment (infrastructure and other)
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	45 years