Goodwill and Other Identifiable Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Goodwill And Other Intangible Assets [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired		$ 59.5		$ 59.5	$ 0.0
Intangible asset amortization expense	$ 24.6		$ 24.3	48.6	$ 48.5
Indefinite-lived Intangible Assets Acquired				$ 19.1
Finite-Lived Intangible Asset, Useful Life				11 years