Goodwill And Intangible Assets (Changes To Intangible Assets) (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Balance at beginning of period, net of accumulated amortization	$ 481.8	$ 276.8
Finite and Indefinite-lived intangible assets acquired	0.0	252.8
Amortization expense	(10.3)	(44.5)
Finite Lived Intangible Assets, Foreign Currency Translation Gain (Loss)	(0.5)	(3.3)
Balance at end of period, net of accumulated amortization	$ 471.0	$ 481.8