Components of Pension Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 91.3	$ 67.3	$ 73.5
Interest on projected benefit obligation	92.2	91.8	81.0
Expected return on assets	(140.8)	(128.0)	(119.4)
Amortization of prior service costs	1.3	1.2	1.3
Recognized actuarial loss	41.1	20.8	44.0
Curtailment gain	(0.1)		(0.3)
Net pension expense	$ 85.0	$ 53.1	$ 80.1