Retirement Benefit Plans - Components of Net Pension Expense (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Compensation and Retirement Disclosure [Abstract]
Service cost	$ 7.6	$ 6.3	$ 22.8	$ 19.0
Interest cost	7.2	6.1	18.3	18.4
Expected return on plan assets	(12.3)	(10.1)	(34.1)	(30.4)
Amortization of prior service cost	(1.1)	(1.0)	(3.4)	(2.9)
Amortization of unrecognized actuarial loss	5.0	2.9	13.5	8.6
Net periodic pension expense	$ 6.4	$ 4.2	$ 17.1	$ 12.7