Note 11 - Derivative Instruments (Details) - Summary of Forward Sales Contracts (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014 lb	Dec. 31, 2013 lb
2014 Settlements [Member] | Silver [Member]
Contracts on provisional sales
Ounces Under Contract (in Pounds)	1,590,000	673,000
Average Price Per Ounce	$ 20.15	$ 19.50
Average Price Per Pound	20.15	19.50
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
2014 Settlements [Member] | Gold [Member]
Contracts on provisional sales
Ounces Under Contract (in Pounds)	7,000	3,000
Average Price Per Ounce	1,304	1,205
Average Price Per Pound	1,304	1,205
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
2014 Settlements [Member] | Zinc [Member]
Contracts on provisional sales
Pounds Under Contract (in Pounds)	29,817,000	11,188,000
Average Price Per Ounce	0.91	0.89
Average Price Per Pound	0.91	0.89
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	29,652,000	31,967,000
Average Price Per Pound	0.99	1.00
Average Price Per Ounce	0.99	1.00
2014 Settlements [Member] | Lead [Member]
Contracts on provisional sales
Pounds Under Contract (in Pounds)	9,755,000	3,472,000
Average Price Per Ounce	0.95	1.00
Average Price Per Pound	0.95	1.00
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	21,054,000	34,282,000
Average Price Per Pound	1.05	1.04
Average Price Per Ounce	1.05	1.04
2015 Settlements [Member] | Silver [Member]
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
2015 Settlements [Member] | Gold [Member]
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
2015 Settlements [Member] | Zinc [Member]
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	45,635,000	39,683,000
Average Price Per Pound	0.96	0.96
Average Price Per Ounce	0.96	0.96
2015 Settlements [Member] | Lead [Member]
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	40,179,000	36,982,000
Average Price Per Pound	1.07	1.07
Average Price Per Ounce	1.07	1.07
2016 Settlements [Member] | Silver [Member]
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
2016 Settlements [Member] | Gold [Member]
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
2016 Settlements [Member] | Zinc [Member]
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	9,094,000	3,803,000
Average Price Per Pound	0.94	0.96
Average Price Per Ounce	0.94	0.96
2016 Settlements [Member] | Lead [Member]
Contracts on forecasted sales
Pounds Under Contract (in Pounds)	31,030,000	30,589,000
Average Price Per Pound	1.03	1.03
Average Price Per Ounce	$ 1.03	$ 1.03