Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment, at Cost

Property, plant and equipment, at cost, consist of the following at December 31, 2018 and 2017 (in thousands):

	Useful Lives (Years)	December 31,
		2018		2017
Land	—	$	123,518	$	118,428
Land improvements	10 – 30	63,349		63,328
Buildings and improvements	10 – 45	251,980		245,482
Machinery and equipment(a)	2 – 45	2,780,478		2,627,667
Long-term mineral rights and production equipment costs	7 – 60	696,033		675,832
Construction in progress	—	883,705		393,598
Total(b)		$	4,799,063	$	4,124,335

(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.