Note 10 - Derivative Instruments (Details) - Summary Of Forward Sales Contracts (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2013 lb	Dec. 31, 2012 lb
2014 Settlements [Member] | Silver [Member]
Contracts on provisional sales
Ounces Under Contract	673,000
Average Price Per Ounce (in Dollars)	$ 19.50
Average Price Per Pound (in Dollars)	19.50
2014 Settlements [Member] | Gold [Member]
Contracts on provisional sales
Ounces Under Contract	3,000
Average Price Per Ounce (in Dollars)	1,205
Average Price Per Pound (in Dollars)	1,205
2014 Settlements [Member] | Zinc [Member]
Contracts on provisional sales
Pounds Under Contract	11,188,000
Average Price Per Ounce (in Dollars)	0.89
Average Price Per Pound (in Dollars)	0.89
Contracts on forecasted sales
Pounds Under Contract	31,967,000	30,203,000
Average Price Per Pound (in Dollars)	1.00	0.98
2014 Settlements [Member] | Lead [Member]
Contracts on provisional sales
Pounds Under Contract	3,472,000
Average Price Per Ounce (in Dollars)	1.00
Average Price Per Pound (in Dollars)	1.00
Contracts on forecasted sales
Pounds Under Contract	34,282,000	33,069,000
Average Price Per Pound (in Dollars)	1.04	1.03
2015 Settlements [Member] | Zinc [Member]
Contracts on forecasted sales
Pounds Under Contract	39,683,000	3,307,000
Average Price Per Pound (in Dollars)	0.96	1.01
2015 Settlements [Member] | Lead [Member]
Contracts on forecasted sales
Pounds Under Contract	36,982,000	23,534,000
Average Price Per Pound (in Dollars)	1.07	1.06
2016 Settlements [Member] | Zinc [Member]
Contracts on forecasted sales
Pounds Under Contract	3,803,000
Average Price Per Pound (in Dollars)	0.93
2016 Settlements [Member] | Lead [Member]
Contracts on forecasted sales
Pounds Under Contract	30,589,000
Average Price Per Pound (in Dollars)	1.03
2013 Settlements [Member] | Zinc [Member]
Contracts on provisional sales
Pounds Under Contract		14,991,000
Average Price Per Ounce (in Dollars)		0.95
Average Price Per Pound (in Dollars)		0.95
Contracts on forecasted sales
Pounds Under Contract		35,935,000
Average Price Per Pound (in Dollars)		0.96
2013 Settlements [Member] | Lead [Member]
Contracts on provisional sales
Pounds Under Contract		6,945,000
Average Price Per Ounce (in Dollars)		1.00
Average Price Per Pound (in Dollars)		1.00
Contracts on forecasted sales
Pounds Under Contract		32,794,000
Average Price Per Pound (in Dollars)		$ 1.11