Information Related to Vesting of Restricted Stock Awards (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Tax benefit realized upon vesting	$ 26.0	$ 43.2	$ 41.1
Restricted Stock [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Fair value of vested shares	111.9	92.4	54.6
Tax benefit realized upon vesting	$ 38.1	$ 31.2	$ 19.3