Components of Net Periodic Benefit Cost (Detail) - Pension Plans, Defined Benefit - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 6.0	$ 5.3
Interest cost	5.3	5.3
Expected return on plan assets	(5.3)	(5.1)
Amortization prior service credit	0.1	(0.2)
Amortization of actuarial loss	2.0	1.5
Net Periodic Benefit Cost	$ 8.1	$ 6.8