Note 3 - Properties, Plants, Equipment and Mineral Interests, and Lease Commitments (Tables)

12 Months Ended

Dec. 31, 2015

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment [Table Text Block]

	December 31,
	2015		2014
Mining properties, including asset retirement obligations	$	372,935	$	336,962
Development costs		291,780		250,340
Plants and equipment		738,065		698,100
Land		21,362		15,799
Mineral interests		907,791		929,844
Construction in progress		295,155		224,216
		2,627,088		2,455,261
Less accumulated depreciation, depletion and amortization		730,277		623,697
Net carrying value	$	1,896,811	$	1,831,564

Operating Leases of Lessee Disclosure [Table Text Block]

Year ending December 31,
2016	$	5,046
2017		3,035
2018		1,049
2019		1,043
2020		1,035
Thereafter		1,196
Total	$	12,404