Note 10 - Derivative Instruments (Tables)

12 Months Ended

Dec. 31, 2015

Derivative Instruments and Hedging Activities Disclosure [Abstract]

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

December 31, 2015	Ounces/pounds under contract (in 000's)								Average price per ounce/pound
	Silver (ounces)		Gold (ounces)		Zinc (pounds)		Lead (pounds)		Silver (ounces)		Gold (ounces)		Zinc (pounds)		Lead (pounds)
Contracts on provisional sales
2016 settlements		1,368		5		23,755		8,433	$	14.12	$	1,076	$	0.71	$	0.77

December 31, 2014	Ounces/pounds under contract (in 000's)								Average price per ounce/pound
	Silver (ounces)		Gold (ounces)		Zinc (pounds)		Lead (pounds)		Silver (ounces)		Gold (ounces)		Zinc (pounds)		Lead (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		N/A		N/A		46,738		29,652		N/A		N/A	$	0.96	$	1.07
2016 settlements		N/A		N/A		44,699		34,337		N/A		N/A	$	0.99	$	1.03
2017 settlements		N/A		N/A		1,984		—		N/A		N/A	$	1.04		N/A