Property Plant Equipment and Mineral Rights and Reserves (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Depreciation and depletion charged to income
Depreciation expense	$ 39.3	$ 35.0	$ 30.1
Depletion expense	1.6	2.6	1.2
Depreciation and depletion	$ 40.9	$ 37.6	$ 31.3