Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment, at Cost

Property, plant and equipment, at cost, consist of the following at December 31, 2017 and 2016 (in thousands):

	Useful Lives (Years)	December 31,
		2017		2016
Land	—	$	118,428	$	120,842
Land improvements	10 – 30	63,328		59,387
Buildings and improvements	10 – 45	245,482		256,603
Machinery and equipment(a)	2 – 45	2,627,667		2,501,481
Long-term mineral rights and production equipment costs	7 – 60	675,832		654,006
Construction in progress	—	393,598		318,203
Total(b)		$	4,124,335	$	3,910,522

(a) Consists primarily of (1) short-lived production equipment components, office and building equipment and other equipment with estimated lives ranging 2 – 7 years, (2) production process equipment (intermediate components) with estimated lives ranging 8 – 19 years, (3) production process equipment (major unit components) with estimated lives ranging 20 – 29 years, and (4) production process equipment (infrastructure and other) with estimated lives ranging 30 – 45 years.

(b) As of December 31, 2017, $215.9 million of Property, plant and equipment, at cost, was classified as Assets held for sale in the consolidated balance sheets. See Note 3, “Divestitures,” for additional information.