Goodwill and Other Intangible Assets - Components of Other Intangible Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount, total other intangible assets	$ 576.7	$ 582.6
Accumulated Amortization, total other intangible assets	(471.1)	(469.3)
Net Book Value, total other intangible assets	105.6	113.3
Client Relationships
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount, total other intangible assets	518.3	520.3
Accumulated Amortization, total other intangible assets	(429.1)	(425.5)
Net Book Value, total other intangible assets	89.2	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	24.6	25.7
Accumulated Amortization, total other intangible assets	(24.4)	(25.2)
Net Book Value, total other intangible assets	0.2	0.5
Trade Names
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount, total other intangible assets	31.8	34.6
Accumulated Amortization, total other intangible assets	(15.6)	(16.6)
Net Book Value, total other intangible assets	$ 16.2	$ 18.0