Property, Plant and Mine Development (Tables)

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Mine Development

At December 31, 2019 and December 31, 2018, property, plant and mine development (in thousands) consisted of the following:

	December 31,   2019			December 31,    2018
Mining property and mine development	$	794,899		$	995,759
Asset retirement cost	18,260			12,732
Land	57,082			55,502
Land improvements	73,203			67,729
Buildings	69,112			64,515
Machinery and equipment	1,152,898			958,357
Furniture and fixtures	4,068			3,599
Construction-in-progress	54,675			167,933
	2,224,197			2,326,126
Accumulated depletion, depreciation, amortization and impairment charges	(706,610		)	(499,823		)
Total property, plant and mine development, net	$	1,517,587		$	1,826,303