Retirement Benefit Plans - Reconciliation of Beginning and Ending Balances of Foreign Pension Plan Assets Measured at Fair Value (Detail) - Foreign-based Defined Benefit Plans [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Schedule of Fair Values of Plan Assets [Line Items]
Plan assets at fair market value - beginning of year	$ 507.0	$ 505.6
Translation gain	26.4	(40.4)
Plan assets at fair market value - end of year	574.9	507.0
Fair Value Measurements at Reporting Date Using: Significant Unobservable Inputs (Level 3) [Member]
Schedule of Fair Values of Plan Assets [Line Items]
Plan assets at fair market value - beginning of year	78.7
Gains on assets sold	0.3
Change in fair value of assets	3.8
Net purchases and sales	5.2
Translation gain	3.0
Plan assets at fair market value - end of year	$ 91.0	$ 78.7