Property, Plant and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 2,141.4	$ 2,167.3
Less: accumulated depreciation and depletion	(1,089.6)	(1,063.0)
Property, plant and equipment, net	1,051.8	1,104.3
Depreciation and depletion expense	75.4	82.1	$ 76.6
Mineral Rights and Reserves [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	547.8	553.8
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	42.7	39.8
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	195.6	179.7
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,193.6	1,130.7
Furniture and Fixtures and Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	123.3	209.7
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 38.4	$ 53.6