Retirement Benefit Plans - Components of Net Pension Expense (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Service cost	$ 7.5	$ 7.6
Interest cost	7.2	5.5
Expected return on plan assets	(12.7)	(10.9)
Curtailment gain	(0.3)
Amortization of prior service cost	(1.9)	(1.1)
Amortization of unrecognized actuarial loss	5.0	4.3
Net periodic pension expense	$ 4.8	$ 5.4