Note 11 - Derivative Instruments (Details) - Summary of Forward Sales Contracts (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2015 oz	Dec. 31, 2014 oz
Silver [Member] | 2015 Settlements [Member]
Contracts on provisional sales
Ounces under contract (in Ounces)	1,587	1,607
Average price per ounce	$ 16.71	$ 16.06
Average price per pound	16.71	16.06
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
Gold [Member] | 2015 Settlements [Member]
Contracts on provisional sales
Ounces under contract (in Ounces)	6	6
Average price per ounce	1,194	1,195
Average price per pound	1,194	1,195
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
Zinc [Member] | 2015 Settlements [Member]
Contracts on provisional sales
Pounds under contract (in Pounds)	25,849,000	19,456,000
Average price per ounce	0.94	1.01
Average price per pound	0.94	1.01
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	27,999,000	46,738,000
Average Price Per Pound	0.95	0.96
Average Price Per Ounce	0.95	0.96
Zinc [Member] | 2016 Settlements [Member]
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	44,699,000	44,699,000
Average Price Per Pound	0.99	0.99
Average Price Per Ounce	0.99	0.99
Zinc [Member] | 2017 Settlements [Member]
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	1,984,000	1,984,000
Average Price Per Pound	1.04	1.04
Average Price Per Ounce	1.04	1.04
Lead [Member] | 2015 Settlements [Member]
Contracts on provisional sales
Pounds under contract (in Pounds)	8,874,000	8,378,000
Average price per ounce	0.81	0.87
Average price per pound	0.81	0.87
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	22,487,000	29,652,000
Average Price Per Pound	1.10	1.07
Average Price Per Ounce	1.10	1.07
Lead [Member] | 2016 Settlements [Member]
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	34,337,000	34,337,000
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