Commitments and Contingent Liabilities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			3 Months Ended				3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Mar. 31, 2012 Vermiculite Related Matters plant	Dec. 31, 2011 Vermiculite Related Matters plant	Mar. 31, 2012 Non-Vermiculite Related Matters	Dec. 31, 2011 Non-Vermiculite Related Matters	Mar. 31, 2012 Multi-Site Settlement claim site
Environmental remediation
Estimated liability for environmental investigative and remediation costs	$ 147.5		$ 151.2	$ 64.6	$ 67.2	$ 82.9	$ 84.0
Net cash expenditures	4.4	2.4
Maximum number of operating plants under U.S. Environmental Protection Agency (EPA) reinvestigation				105
Number of facilities that expanded Libby vermiculite					7
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