Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Income taxes	$ 43.9	$ (13.3)	$ 114.8	$ 76.9
Effective income tax rate	31.90%	647.90%	31.10%	27.20%
Utilization of deferred tax asset interest expense	$ (240.8)
Total amount of unrecognized tax benefits, including related interest and penalties	57.7		$ 57.7
Unrecognized tax benefits excluding interest and penalties that if recognized would affect the effective tax rate	45.5		45.5
Total accrued interest for tax contingencies	7.0		7.0
Total accrued penalties for tax contingencies	1.4		1.4
Amount of unrecognized tax benefits that could decrease within the next 12 months	12.7		12.7
Decrease in unrecognized tax benefits due to the settlement of audits or resolution of administrative or judicial proceedings	5.7		5.7
Decrease in unrecognized tax benefits expiration of statute of limitations	$ 7.0		$ 7.0