Goodwill And Intangible Assets (Changes To Intangible Assets) (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Balance at beginning of period, net of accumulated amortization	$ 276.8	$ 282.2
Finite and Indefinite-lived intangible assets acquired	250.8	18.2
Amortization expense	(11.7)	(30.9)
Finite Lived Intangible Assets, Foreign Currency Translation Gain (Loss)	5.1	7.3
Balance at end of period, net of accumulated amortization	$ 521.0	$ 276.8