Note 11 - Business Segments and Significant Customers (Details Textual) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Number of Reportable Segments	4
Derivative, Loss on Derivative	$ 6,000	$ 14,200
Derivative, Gain on Derivative			$ 6,200
Employee Labor Strike Related Costs	21,301
Lucky Friday [Member] | Suspension Costs [Member]
Employee Labor Strike Related Costs	17,100
Lucky Friday [Member] | Non-cash Depreciation Expense [Member]
Employee Labor Strike Related Costs	$ 4,200