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Note 13. Asset Retirement Obligations (Detail) (USD $)					9 Months Ended
Note 13. Asset Retirement Obligations (Detail) (USD $)	Sep. 30, 2012	Dec. 31, 2011	Dec. 31, 2010	Sep. 30, 2012 Greens Creek [Member]	Sep. 30, 2012 Minimum [Member]	Sep. 30, 2012 Maximum [Member]
Accrual for Environmental Loss Contingencies	$ 148,100,000	$ 153,800,000
Risk Free Interest Rate					4.00%	7.00%
Asset Retirement Obligation	38,219,000	37,643,000	36,397,000	36,900,000
Mine Reclamation and Closing Liability, Noncurrent				53,400,000
Reclamation Bond Potential Increase	$ 30,000,000

Total costs accrued as of the balance sheet date for environmental loss contingencies.

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- Definition

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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