Contingencies Contingencies (Details) (USD $)		3 Months Ended
	Nov. 30, 2011	Sep. 30, 2011 Pending Litigation [Member] Environmental Issue [Member] General and Administrative Expense [Member] New Idria Mercury Mine [Member]	Sep. 30, 2011 Other Liabilities [Member] Pending Litigation [Member] Environmental Issue [Member] New Idria Mercury Mine [Member]
Loss Contingencies [Line Items]
Expense related to remedial investigation and feasibility study		$ 1,900,000
Expenses incurred and charged against reserve			300,000
Estimate of EPA's interim removal project costs	$ 500,000