Retirement Benefit Plans - Components of Net Periodic Pension Expense (Detail) - US and Foreign [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule of Expected Future Pension Benefit Payment [Line Items]
Service cost	$ 7.0	$ 6.4	$ 14.5	$ 13.9
Interest cost	5.6	4.6	11.1	9.3
Expected return on plan assets	(11.7)	(10.1)	(23.5)	(20.2)
Curtailment loss		0.2		0.2
Amortization of prior service cost	(2.5)	(2.5)	(5.0)	(5.1)
Amortization of unrecognized actuarial loss	6.7	5.2	12.8	10.8
Net periodic pension expense	$ 5.1	$ 3.8	$ 9.9	$ 8.9