Note 4 - Commitments, Contingencies and Obligations (Detail)	1 Months Ended							3 Months Ended							3 Months Ended					1 Months Ended
	Aug. 30, 2014 USD ($)	Oct. 31, 2013 USD ($)	Apr. 30, 2013 USD ($)	Mar. 31, 2013 USD ($)	Mar. 31, 2013 CAD	Aug. 31, 2012 USD ($)	Jun. 30, 2011 USD ($)	Mar. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Mar. 31, 2012 USD ($)	May 07, 2013 USD ($)	May 07, 2013 CAD	Apr. 12, 2013	Apr. 30, 2009 USD ($)	Mar. 31, 2013 Greens Creek [Member] USD ($)	Mar. 31, 2013 Lucky Friday [Member] USD ($)	Mar. 31, 2013 Non-Capital Costs [Member] USD ($)	Dec. 31, 2012 Minimum [Member] USD ($)	Dec. 31, 2012 Maximum [Member] USD ($)	Jan. 31, 2010 Costs Incurred By The EPA [Member] USD ($)
Maximum Environmental Remediation Obligation								$ 2,500,000
Loss Contingency, Estimate of Possible Loss														177,500				0	10,000,000
Payment Of Response Costs						1,100,000			1,100,000
Other Accrued Liabilities, Noncurrent									300,000
Estimated Response Costs							4,500,000
Estimated Future Response Cost							100,000,000
Incurred Response Costs																				200,000,000
Business Acquisition, Share Price (in Dollars per share)					4.75
Business Acquisition Per Share Issued (in Shares)				0.9953	0.9953
Business Acquisition, Cost of Acquired Entity, Purchase Price (in Dollars and Dollars)					513,600,000						695,500,000	700,900,000
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares (in Shares)				57,000,000	57,000,000
Proceeds from Issuance of Debt			500,000,000
Debt Instrument, Interest Rate, Stated Percentage			6.875%										6.875%
Contractual Obligations				10,300,000				10,300,000									1,800,000
Open Purchase Orders															2,400,000	300,000
Noncapital Costs															300,000	300,000
Commitments For Capital Lease Payments				23,600,000				23,600,000
Environmental Expense and Liabilities	55,400,000	15,000,000						591,000		1,427,000
Letters of Credit Outstanding, Amount				$ 1,200,000				$ 1,200,000