Property, Plant, Equipment and Mineral Rights and Reserves - Depreciation and Depletion Charged to Income (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Depreciation and depletion charged to income [Abstract]
Depreciation expense	$ 44.1	$ 39.3	$ 35.0
Depletion expense	1.5	1.6	2.6
Depreciation and depletion	$ 45.6	$ 40.9	$ 37.6