Stock-Based Compensation Expense and Associated Tax Benefit (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Stock-based compensation expense	$ 87.2	$ 80.4	$ 67.1
Tax benefit	$ 28.6	$ 27.5	$ 24.7