Note 4. Commitments, Contingencies and Obligations (Detail) (USD $)	1 Months Ended					3 Months Ended
	Feb. 29, 2012	Jun. 30, 2011	Apr. 30, 2011	Jan. 31, 2010	Apr. 30, 2009	Mar. 31, 2012	Mar. 31, 2011	Oct. 31, 2011	Sep. 08, 2011
Maximum Environmental Remediation Obligation						$ 2,500,000
AdministrativePenalty					177,500
IncurredResponseCosts				91,000,000
EstimatedFutureResponseCost		100,000,000		72,000,000
ContributionAndCostRecovery			9,000,000
Payments to Acquire Land	1,875,000
Other Accrued Liabilities, Noncurrent						900,000
Increase (Decrease) in Other Accrued Liabilities						(3,659,000)	(1,378,000)
EstimatedResponseCosts		4,500,000
Contractual Obligations						6,200,000
Noncapital Costs						17,500,000
Commitments for Capital Lease Payments						14,400,000
Environmental Litigation and Related Claims									95,400,000
Letters of Credit Outstanding, Amount						600,000
Annual Maintenance Fee								600,000
United Steel Workers Claims Lower Range						0
UnitedSteelWorkersClaimsUpperRange						10,000,000
Johnny M Mine [Member]
Increase (Decrease) in Other Accrued Liabilities						700,000
Greens Creek [Member]
Open Purchase Orders						10,000,000
Lucky Friday [Member]
Open Purchase Orders						900,000
Greens Creek [Member]
Noncapital Costs						2,700,000
Lucky Friday [Member]
Noncapital Costs						$ 200,000