Goodwill and Identifiable Intangible Assets, Net - Summary of Identifiable Intangible Assets with Definite and Indefinite Useful Lives (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 172.0	$ 113.2
Accumulated Amortization	(97.3)	(82.0)
Net	74.7	31.2
Indefinite-lived intangible assets
Total identifiable intangible assets, Gross Carrying Value	180.9	122.1
Total identifiable intangible assets, Net	83.6	40.1
Trademarks and tradenames with indefinite lives
Indefinite-lived intangible assets
Trademarks and tradenames with indefinite lives, Gross Carrying Value	8.9	8.9
Trademarks and tradenames with indefinite lives, Net	8.9	8.9
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	59.7	25.0
Accumulated Amortization	(19.7)	(17.5)
Net	40.0	7.5
Trademarks and tradenames
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	11.6	0.6
Accumulated Amortization	(0.5)	(0.2)
Net	11.1	0.4
Capitalized Software
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	50.6	42.6
Accumulated Amortization	(40.0)	(31.2)
Net	10.6	11.4
Technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	39.2	34.4
Accumulated Amortization	(27.5)	(24.2)
Net	11.7	10.2
Customer Contracts
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	10.9	10.6
Accumulated Amortization	(9.6)	(8.9)
Net	$ 1.3	$ 1.7