Note 4. Commitments, Contingencies and Obligations (Detail) (USD $)	1 Months Ended					9 Months Ended
	Oct. 31, 2012	Feb. 29, 2012	Jun. 30, 2011	Jan. 31, 2010	Apr. 30, 2009	Sep. 30, 2012	Jun. 30, 2012	Oct. 31, 2011
Maximum Environmental Remediation Obligation						$ 2,500,000
AdministrativePenalty					177,500
Payments to Acquire Land		1,875,000
EstimatedResponseCosts			4,500,000
EstimatedFutureResponseCost			100,000,000	72,000,000
IncurredResponseCosts				91,000,000
Noncapital Costs						25,000,000
Commitments for Capital Lease Payments						15,500,000
Payments for Environmental Liabilities	25,000,000
Environmental Litigation and Related Claims						70,500,000
Annual Maintenance Fee								600,000
Letters of Credit Outstanding, Amount						600,000
United Steel Workers Claims Lower Range							0
UnitedSteelWorkersClaimsUpperRange							10,000,000
Lucky Friday [Member]
Contractual Obligations						11,100,000
Greens Creek [Member]
Contractual Obligations						200,000
Barker-Hughesville Site [Member]
ContributionAndCostRecovery						9,000,000
Black Pine Mine Site [Member]
ContributionAndCostRecovery						17,700,000
Van Stone Mine Site [Member]
ContributionAndCostRecovery						3,500,000
Greens Creek [Member]
Noncapital Costs						600,000
Environmental Protection Agency [Member]
Other Accrued Liabilities, Noncurrent						1,100,000
Estimated Past Costs And Investigation And Planning Costs [Member]
Other Accrued Liabilities, Noncurrent						1,400,000
Greens Creek [Member]
Open Purchase Orders						10,700,000
Lucky Friday [Member]
Open Purchase Orders						$ 1,400,000