Components of Pension Expense (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 21.9	$ 21.6
Interest on projected benefit obligation	23.6	22.9
Expected return on assets	(35.6)	(34.8)
Amortization of prior service costs	0.3	0.3
Recognized actuarial loss	6.5	10.1
Net pension expense	$ 16.7	$ 20.1