Income Taxes (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Company's effective tax rate	29.40%	33.00%	29.40%	29.40%
Federal statutory income tax rate	35.00%
Unrecognized Tax Benefits, Period Increase (Decrease)	$ 0.1
Increase In Unrecognized Tax Benefits That Would Impact Effective Tax Rate	0.1		$ 2.7
Recognized interest expense related to unrecognized tax benefits	0.1		0.6
Interest and penalty related to unrecognized tax benefits recorded	6.8		6.8		$ 6.2
Reasonable possible increase in unrecognized tax benefits during the next twelve months	$ (7.7)		$ (7.7)