Goodwill and Other Identifiable Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Goodwill And Other Intangible Assets [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired			$ 59.5	$ 0.0
Intangible asset amortization expense	$ 24.6	$ 24.1	73.2	$ 72.6
Indefinite-lived Intangible Assets Acquired			$ 19.1
Finite-Lived Intangible Asset, Useful Life			11 years