Income Taxes - Schedule of Deferred Income Tax Expense (Benefit) Attributable to Income from Continuing Operations (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Deferred income tax (benefit) expense	$ 77.6	$ (51.9)	$ (71.9)
Change in valuation allowance	2.1	31.8	6.7
Change in effective U.S. state income tax rate	(2.9)	(7.2)	3.0
Change in effective foreign income tax rate	3.3	(5.0)	0.3
Deferred Income Tax Expense (Benefit)	$ 80.1	$ (32.3)	$ (61.9)