Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefit (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	$ 12.3	$ 11.9
Additions for Tax Positions Taken in Prior Years	6.6	3.9
Reductions for Tax Positions Taken in Prior Years	(1.2)	(2.7)
Reductions Resulting from Expiration of Statutes	(0.5)	(0.8)
Ending Balance	$ 17.2	$ 12.3