Goodwill and Other Intangible Assets - Components of Other Intangible Assets (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount, total other intangible assets	$ 575.4	$ 582.6
Accumulated Amortization, total other intangible assets	(468.5)	(469.3)
Net Book Value, total other intangible assets	106.9	113.3
Client Relationships
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount, total other intangible assets	513.5	520.3
Accumulated Amortization, total other intangible assets	(424.5)	(425.5)
Net Book Value, total other intangible assets	89.0	94.8
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	25.2	25.7
Accumulated Amortization, total other intangible assets	(24.8)	(25.2)
Net Book Value, total other intangible assets	0.4	0.5
Trade Names
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount, total other intangible assets	34.7	34.6
Accumulated Amortization, total other intangible assets	(17.2)	(16.6)
Net Book Value, total other intangible assets	$ 17.5	$ 18.0