Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Useful Lives Of Depreciable Assets

The provision for depreciation has been computed principally by the straight-line method based on the estimated useful lives of the depreciable assets as follows:

Category	Useful Life
Buildings	30 years
Leased assets and leasehold improvements	Amortized over the lesser of the economic life of the asset or the term of the lease
Machinery and equipment	3 – 10 years

The classes of property, plant and equipment as of December 31 are summarized as follows ($ in millions):

	2019			2018
Land and improvements	$	23.7		$	24.7
Buildings	166.9			152.4
Machinery and equipment	502.3			459.7
Gross property, plant and equipment	692.9			636.8
Less: accumulated depreciation	(402.6		)	(375.2		)
Property, plant and equipment, net	$	290.3		$	261.6