Note 10 - Derivative Instruments (Tables)

6 Months Ended

12 Months Ended

Jun. 30, 2013

Dec. 31, 2012

Derivative Instruments and Hedging Activities Disclosure [Abstract]

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

June 30, 2013	Pounds under contract (in thousands)				Average price per pound
	Zinc		Lead		Zinc		Lead
Contracts on provisional sales
2013 settlements		19,786		9,314	$	0.85	$	0.92
Contracts on forecasted sales
2013 settlements		15,046		14,936	$	0.96	$	1.05
2014 settlements		60,516		47,619	$	0.99	$	1.05
2015 settlements		26,896		39,628	$	0.98	$	1.07

December 31, 2012	Pounds under contract (in thousands)				Average price per pound
	Zinc		Lead		Zinc		Lead
Contracts on provisional sales
2013 settlements		14,991		6,945	$	0.95	$	1.00
Contracts on forecasted sales
2013 settlements		35,935		32,794	$	0.96	$	1.11
2014 settlements		30,203		33,069	$	0.98	$	1.03
2015 settlements		3,307		23,534	$	1.01	$	1.06

December 31, 2012	Pounds under contract (in thousands)				Average price per pound
	Zinc		Lead		Zinc		Lead
Contracts on provisional sales
2013 settlements		14,991		6,945	$	0.95	$	1.00
Contracts on forecasted sales
2013 settlements		35,935		32,794	$	0.96	$	1.11
2014 settlements		30,203		33,069	$	0.98	$	1.03
2015 settlements		3,307		23,534	$	1.01	$	1.06

December 31, 2011	Pounds under contract (in thousands)				Average price per pound
	Zinc		Lead		Zinc		Lead
Contracts on provisional sales
2012 settlements		21,164		5,732	$	0.86	$	0.89
Contracts on forecasted sales
2012 settlements		45,195		35,053	$	1.12	$	1.12
2013 settlements		18,243		24,582	$	1.14	$	1.17