Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Taxes [Line Items]
Income tax expense	$ 142.2	$ 88.8	$ 261.5	$ 176.9
Effective tax rate	34.60%	32.80%	34.40%	32.80%