Commitments and Contingent Liabilities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			12 Months Ended					3 Months Ended
	Mar. 31, 2013 site	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2012 Vermiculite Related Matters facility	Dec. 31, 2010 Vermiculite Related Matters facility	Mar. 31, 2013 Vermiculite Related Matters	Mar. 31, 2013 Non-Vermiculite Related Matters	Dec. 31, 2012 Non-Vermiculite Related Matters	Mar. 31, 2013 Multi-Site Settlement site claim
Environmental remediation
Estimated liability for environmental investigative and remediation costs	$ 139.9		$ 141.5	$ 60.8		$ 60.3	$ 79.6	$ 80.7
Net cash expenditures	2.6	4.4
Maximum number of operating plants under U.S. Environmental Protection Agency (EPA) reinvestigation					105
Number of facilities expanded				8
Number of sites for potential contamination claims under U.S. Environmental Protection Agency (EPA) investigation									38
Amount agreed to pay in settlement of outstanding claims									$ 44
Number of outstanding claims settled									35
Number of remaining sites for remediation	2