Stock-Based Compensation Cost and Associated Tax Benefit (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Stock compensation cost	$ 21.7	$ 20.3	$ 44.4	$ 40.6
Tax benefit	$ 6.7	$ 6.5	$ 14.6	$ 12.8