Acquired Intangible Assets and Related Amortization (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Finite Lived Intangible Assets [Line Items]
Acquired intangible assets, net	$ 1,641.6	$ 1,631.6
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Acquired intangible assets, gross	1,371.7	1,345.1
Accumulated amortization	(175.4)	(159.9)
Acquired intangible assets, net	1,196.3	1,185.2
Trade Secrets [Member]
Finite Lived Intangible Assets [Line Items]
Acquired intangible assets, gross	30.1	30.2
Accumulated amortization	(28.1)	(28.1)
Acquired intangible assets, net	2.0	2.1
Computer Software Intangible Asset [Member]
Finite Lived Intangible Assets [Line Items]
Acquired intangible assets, gross	366.1	358.6
Accumulated amortization	(86.7)	(78.0)
Acquired intangible assets, net	279.4	280.6
Trade Names [Member]
Finite Lived Intangible Assets [Line Items]
Acquired intangible assets, gross	164.6	161.6
Accumulated amortization	(29.2)	(26.7)
Acquired intangible assets, net	135.4	134.9
Other Intangible Assets [Member]
Finite Lived Intangible Assets [Line Items]
Acquired intangible assets, gross	58.2	57.4
Accumulated amortization	(29.7)	(28.6)
Acquired intangible assets, net	$ 28.5	$ 28.8