Components of Pension Expense (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 22.6	$ 24.2	$ 44.5	$ 45.8
Interest on projected benefit obligation	24.1	23.3	47.7	46.2
Expected return on assets	(36.1)	(35.7)	(71.7)	(70.5)
Amortization of prior service costs	0.3	0.3	0.6	0.6
Recognized actuarial loss	7.4	10.5	13.9	20.6
Net pension expense	$ 18.3	$ 22.6	$ 35.0	$ 42.7