Goodwill and Other Identifiable Intangible Assets - Detail of Identifiable Intangible Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Acquired Intangible Assets By Major Class [Line Items]
Cost	$ 469.0	$ 460.4
Accumulated amortization	(322.7)	(294.6)
Net	146.3	165.8
Cost	646.0	633.8
Net	323.3	339.2
Customer relationships
Acquired Intangible Assets By Major Class [Line Items]
Cost	426.1	418.1
Accumulated amortization	(294.6)	(269.1)
Net	131.5	149.0
Proprietary technology and patents
Acquired Intangible Assets By Major Class [Line Items]
Cost	42.9	42.3
Accumulated amortization	(28.1)	(25.5)
Net	14.8	16.8
Trade names intangibles
Acquired Intangible Assets By Major Class [Line Items]
Net, indefinite-life intangibles	$ 177.0	$ 173.4