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

12 Months Ended

Dec. 31, 2019

Notes Tables

Property, Plant and Equipment [Table Text Block]

	December 31,
	2019		2018
Mining properties, including asset retirement obligations	$	762,355	$	533,631
Development costs		503,111		444,229
Plants and equipment		1,056,512		988,285
Land		32,909		32,953
Mineral interests		1,018,380		1,269,956
Construction in progress		360,827		365,807
		3,734,094		3,634,861
Less accumulated depreciation, depletion and amortization		1,310,396		1,114,857
Net carrying value	$	2,423,698	$	2,520,004