Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Income Tax [Line Items]
Effective income tax rate	17.20%	23.40%	14.20%	21.40%
Income tax provision	$ (29.1)	$ (48.5)	$ (52.5)	$ (75.2)
Unrecognized tax benefits related to federal, state and foreign taxes	20.5		20.5		$ 21.5
Unrecognized tax benefits that would impact effective tax rate	17.4		17.4
Accrued interest	3.3		3.3		$ 2.6
Decrease in unrecognized tax benefits within the next 12 months	5.0		$ 5.0
Number of months unrecognized tax benefits may decrease			12 months
New Accounting Pronouncement, 2016-09
Income Tax [Line Items]
Income tax provision	$ 10.5		$ 37.5