Income Taxes (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit)	$ 1.0	$ 87.0		$ 0.0
Company's effective tax rate	23.10%		30.50%	21.10%	29.40%
Unrecognized Tax Benefits, Period Increase (Decrease)	$ 0.7			$ 0.8
Increase In Unrecognized Tax Benefits That Would Impact Effective Tax Rate	1.0			1.4
Recognized interest expense related to unrecognized tax benefits	0.6			1.0
Interest and penalty related to unrecognized tax benefits recorded	7.5	6.5		7.5
Reasonable possible increase in unrecognized tax benefits during the next twelve months	$ (14.7)			$ (14.7)
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense		75.0
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Liability		$ 12.0