Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

The components of inventories were as follows (dollars in millions):


	December 31,
	2023		2022
Raw materials	$	326.2	$	341.2
Work in process		14.9		16.0
Finished goods		200.5		198.4
Supplies and materials		471.5		421.7
Inventories	$	1,013.1	$	977.3

Summary of Property, Plant and Equipment (at cost)

Property, plant, and equipment consisted of the following (dollars in millions):


	December 31,
	2023			2022
Land and land improvements	$	197.8		$	192.4
Buildings		1,090.4			1,023.6
Machinery and equipment		7,006.7			6,709.3
Construction in progress		335.8			440.2
Other		177.0			146.9
Property, plant and equipment, at cost		8,807.7			8,512.4
Less accumulated depreciation		(4,943.9	)		(4,612.4	)
Property, plant and equipment, net	$	3,863.8		$	3,900.0

Summary of Property, Plant and Equipment Estimated Useful Lives

Depreciation is computed on the straight-line basis over the estimated useful lives of the related assets. Assets under finance leases are depreciated on the straight-line method over the term of the lease or the useful life, if shorter. The following lives are used for the various categories of assets:


Buildings and land improvements		5 to 40 years
Machinery and equipment		3 to 25 years
Trucks and automobiles		3 to 10 years
Furniture and fixtures		3 to 20 years
Computers and hardware		3 to 10 years
Leasehold improvements		Period of the lease or useful life, if shorter