Summary of Deferred Tax Valuation Allowance (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Balance, beginning of period	$ 382.4	$ 385.6	$ 375.0
Additions (reductions) recorded in the provision for income taxes	23.6	(5.8)	10.6
Business acquired		2.6
Balance, end of period	$ 406.0	$ 382.4	$ 385.6