Components of Pension Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 88.6	$ 91.3	$ 67.3
Interest on projected benefit obligation	94.3	92.2	91.8
Expected return on assets	(141.7)	(140.8)	(128.0)
Amortization of prior service costs	1.2	1.3	1.2
Recognized actuarial loss	27.7	41.1	20.8
Curtailment gain		(0.1)
Net pension expense	$ 70.1	$ 85.0	$ 53.1