Contingencies Contingencies (Details) (USD $) In Millions, unless otherwise specified		3 Months Ended
	Nov. 30, 2011	Sep. 30, 2011 General and Administrative Expense Environmental Issue Pending Litigation New Idria Mercury Mine	Sep. 30, 2011 Other Liabilities Environmental Issue Pending Litigation New Idria Mercury Mine
Loss Contingencies [Line Items]
Expense related to remedial investigation and feasibility study		$ 1.9
Payments charged against the reserve			0.6
Estimate of EPA's interim removal project costs	$ 0.5