Property, Plant and Equipment

12 Months Ended

Dec. 31, 2021

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment

Property, Plant and Equipment:

Property, plant and equipment, at cost, consist of the following at December 31, 2021 and 2020 (in thousands):

	Useful Lives (Years)	December 31,
		2021		2020
Land	—	$	117,703	$	121,330
Land improvements	10 – 30	112,374		115,693
Buildings and improvements	10 – 50	383,879		354,679
Machinery and equipment(a)	2 – 45	3,619,712		3,564,389
Mineral rights and reserves	7 – 60	1,783,691		1,780,236
Construction in progress	—	2,057,387		1,491,314
Total		$	8,074,746	$	7,427,641

(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.

The cost of property, plant and equipment is depreciated generally by the straight-line method. Depletion of mineral rights is based on the units-of-production method. Depreciation expense, including depletion, amounted to $225.6 million, $203.6 million and $183.3 million during the years ended December 31, 2021, 2020 and 2019, respectively. Interest capitalized on significant capital projects in 2021, 2020 and 2019 was $50.0 million, $30.4 million and $30.2 million, respectively.