Note 11 - Summary of Forward Sales Contracts (Details) - 2016 Settlements [Member] oz in Thousands, lb in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2016 lb oz $ / lb $ / oz	Dec. 31, 2015 lb oz $ / lb $ / oz
Silver [Member]
Pounds Under Contract | oz	1,523	1,368
Average Price | $ / oz	17.4	14.12
Gold [Member]
Pounds Under Contract | oz	4	5
Average Price | $ / oz	1,271	1,076
Zinc [Member]
Pounds Under Contract | lb	19,731	23,755
Average Price | $ / lb	0.88	0.71
Lead [Member]
Pounds Under Contract | lb	8,818	8,433
Average Price | $ / lb	0.79	0.77