Note 4 - Properties, Plants, Equipment and Mineral Interests, and Lease Commitments (Tables)

12 Months Ended

Dec. 31, 2020

Notes Tables

Property, Plant and Equipment [Table Text Block]

	December 31,
	2020		2019
Mining properties, including asset retirement obligations	$	818,819	$	762,355
Development costs		526,714		503,111
Plants and equipment		1,129,200		1,056,512
Land		32,983		32,909
Mineral interests		969,589		1,018,380
Construction in progress		347,099		360,827
		3,824,404		3,734,094
Less accumulated depreciation, depletion and amortization		1,479,185		1,310,396
Net carrying value	$	2,345,219	$	2,423,698