Note 10 - Derivative Instruments (Details) - Summary of Forward Sales Contracts (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Silver [Member] | 2015 Settlements [Member]
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
Silver [Member] | 2016 Settlements [Member]
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
Silver [Member] | 2017 Settlements [Member]
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
Silver [Member] | 2014 Settlements [Member]
Contracts on provisional sales
Ounces under contract (in Ounces)		673
Average price per ounce		19.50
Average price per pound		19.50
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
Silver [Member]
Contracts on provisional sales
Ounces under contract (in Ounces)	1,607
Average price per ounce	16.06
Average price per pound	16.06
Gold [Member] | 2015 Settlements [Member]
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
Gold [Member] | 2016 Settlements [Member]
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
Gold [Member] | 2017 Settlements [Member]
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
Gold [Member] | 2014 Settlements [Member]
Contracts on provisional sales
Ounces under contract (in Ounces)		3
Average price per ounce		1,205
Average price per pound		1,205
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
Gold [Member]
Contracts on provisional sales
Ounces under contract (in Ounces)	6
Average price per ounce	1,195
Average price per pound	1,195
Zinc [Member] | 2015 Settlements [Member]
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	46,738,000	39,683,000
Average Price Per Pound	0.96	0.96
Average Price Per Ounce	0.96	0.96
Zinc [Member] | 2016 Settlements [Member]
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	44,699,000	3,803,000
Average Price Per Pound	0.99	0.93
Average Price Per Ounce	0.99	0.93
Zinc [Member] | 2017 Settlements [Member]
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	1,984,000
Average Price Per Pound	1.04
Average Price Per Ounce	1.04
Zinc [Member] | 2014 Settlements [Member]
Contracts on provisional sales
Pounds under contract (in Pounds)		11,188,000
Average price per ounce		0.89
Average price per pound		0.89
Contracts on forecasted sales
Pounds Under Contract (in Pounds)		31,967,000
Average Price Per Pound		1.00
Average Price Per Ounce		1.00
Zinc [Member]
Contracts on provisional sales
Pounds under contract (in Pounds)	19,456,000
Average price per ounce	1.01
Average price per pound	1.01
Lead [Member] | 2015 Settlements [Member]
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	29,652,000	36,982,000
Average Price Per Pound	1.07	1.07
Average Price Per Ounce	1.07	1.07
Lead [Member] | 2016 Settlements [Member]
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	34,337,000	30,589,000
Average Price Per Pound	1.03	1.03
Average Price Per Ounce	1.03	1.03
Lead [Member] | 2017 Settlements [Member]
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
Lead [Member] | 2014 Settlements [Member]
Contracts on provisional sales
Pounds under contract (in Pounds)		3,472,000
Average price per ounce		1.00
Average price per pound		1.00
Contracts on forecasted sales
Pounds Under Contract (in Pounds)		34,282,000
Average Price Per Pound		1.04
Average Price Per Ounce		1.04
Lead [Member]
Contracts on provisional sales
Pounds under contract (in Pounds)	8,378,000
Average price per ounce	0.87
Average price per pound	$ 0.87