Note 11 - Derivative Instruments (Tables)

3 Months Ended

Mar. 31, 2015

Derivative Instruments and Hedging Activities Disclosure [Abstract]

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

March 31, 2015	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		1,587		6		25,849		8,874	$	16.71	$	1,194	$	0.94	$	0.81
Contracts on forecasted sales
2015 settlements		—		—		27,999		22,487		N/A		N/A	$	0.95	$	1.10
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, 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