Goodwill and Other Intangible Assets - Components of Other Intangible Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount, total other intangible assets	$ 471.3	$ 467.2
Accumulated Amortization, total other intangible assets	(402.5)	(378.4)
Net Book Value, total other intangible assets	68.8	88.8
Client Relationships
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount, total other intangible assets	417.0	410.2
Accumulated Amortization, total other intangible assets	(361.1)	(337.1)
Net Book Value, total other intangible assets	55.9	73.1
Patents
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount, total other intangible assets	2.0	2.0
Accumulated Amortization, total other intangible assets	(2.0)	(2.0)
Trademarks, Licenses and Agreements
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount, total other intangible assets	23.2	23.5
Accumulated Amortization, total other intangible assets	(23.2)	(23.5)
Trade Names
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount, total other intangible assets	29.1	31.5
Accumulated Amortization, total other intangible assets	(16.2)	(15.8)
Net Book Value, total other intangible assets	$ 12.9	$ 15.7