Property, Plant and Mine Development (Tables)

3 Months Ended

Mar. 31, 2020

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Mine Development

At March 31, 2020 and December 31, 2019, property, plant and mine development (in thousands) consisted of the following:

	March 31,   2020			December 31,    2019
Mining property and mine development	$	788,574		$	794,899
Asset retirement cost	18,011			18,260
Land	57,494			57,082
Land improvements	74,027			73,203
Buildings	69,373			69,112
Machinery and equipment	1,177,350			1,152,898
Furniture and fixtures	4,071			4,068
Construction-in-progress	42,330			54,675
	2,231,230			2,224,197
Accumulated depletion, depreciation, amortization and impairment charges	(744,009		)	(706,610		)
Total property, plant and mine development, net	$	1,487,221		$	1,517,587