Note 11 - Derivative Instruments (Details) - Summary of Forward Sales Contracts oz in Thousands, lb in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2015 USD ($) oz lb	Dec. 31, 2014 USD ($) oz lb
2015 Settlements [Member] | Silver [Member]
Contracts on provisional sales
Ounces under contract (in Ounces) | oz	1,388	1,607
Average price per ounce	$ 16.45	$ 16.06
Average price per pound	$ 16.45	$ 16.06
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
2015 Settlements [Member] | Gold [Member]
Contracts on provisional sales
Ounces under contract (in Ounces) | oz	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
2015 Settlements [Member] | Zinc [Member]
Contracts on provisional sales
Pounds under contract (in Pounds) | lb	25,298	19,456
Average price per ounce	$ 0.97	$ 1.01
Average price per pound	$ 0.97	$ 1.01
Contracts on forecasted sales
Pounds Under Contract (in Pounds) | lb	13,228	46,738
Average Price Per Pound	$ 0.88	$ 0.96
Average Price Per Ounce	$ 0.88	$ 0.96
2015 Settlements [Member] | Lead [Member]
Contracts on provisional sales
Pounds under contract (in Pounds) | lb	5,567	8,378
Average price per ounce	$ 0.82	$ 0.87
Average price per pound	$ 0.82	$ 0.87
Contracts on forecasted sales
Pounds Under Contract (in Pounds) | lb		29,652
Average Price Per Pound		$ 1.07
Average Price Per Ounce		$ 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) | lb	20,779	44,699
Average Price Per Pound	$ 0.95	$ 0.99
Average Price Per Ounce	$ 0.95	$ 0.99
2016 Settlements [Member] | Lead [Member]
Contracts on forecasted sales
Pounds Under Contract (in Pounds) | lb		34,337
Average Price Per Pound		$ 1.03
Average Price Per Ounce		$ 1.03
2017 Settlements [Member] | Silver [Member]
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
2017 Settlements [Member] | Gold [Member]
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce
2017 Settlements [Member] | Zinc [Member]
Contracts on forecasted sales
Pounds Under Contract (in Pounds) | lb		1,984
Average Price Per Pound		$ 1.04
Average Price Per Ounce		$ 1.04
2017 Settlements [Member] | Lead [Member]
Contracts on forecasted sales
Average Price Per Pound
Average Price Per Ounce