Note 10 - Derivative Instruments (Tables)

12 Months Ended

Dec. 31, 2014

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]

December 31, 2014	Ounces/pounds under contract (in 000's)								Average price per ounce/pound
	Silver		Gold		Zinc		Lead		Silver		Gold		Zinc		Lead
	(ounces)		(ounces)		(pounds)		(pounds)		(ounces)		(ounces)		(pounds)		(pounds)
Contracts on provisional sales
2015 settlements		1,607		6		19,456		8,378	$	16.06	$	1,195	$	1.01	$	0.87
Contracts on forecasted sales
2015 settlements		—		—		46,738		29,652	N/A		N/A		$	0.96	$	1.07
2016 settlements		—		—		44,699		34,337	N/A		N/A		$	0.99	$	1.03
2017 settlements		—		—		1,984		—	N/A		N/A		$	1.04	N/A

December 31, 2013	Ounces/pounds under contract (in 000's)								Average price per ounce/pound
	Silver		Gold		Zinc		Lead		Silver		Gold		Zinc		Lead
	(ounces)		(ounces)		(pounds)		(pounds)		(ounces)		(ounces)		(pounds)		(pounds)
Contracts on provisional sales
2014 settlements		673		3		11,188		3,472		19.50		1,205	$	0.89	$	1.00
Contracts on forecasted sales
2014 settlements		—		—		31,967		34,282	N/A		N/A		$	1.00	$	1.04
2015 settlements		—		—		39,683		36,982	N/A		N/A		$	0.96	$	1.07
2016 settlements		—		—		3,803		30,589	N/A		N/A		$	0.93	$	1.03