Retirement Benefit Plans - Reconciliation of Beginning and Ending Balances of Foreign Pension Plan Assets Measured at Fair Value (Detail) - Foreign [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Schedule of Fair Values of Plan Assets [Line Items]
Plan assets at fair market value - beginning of year	$ 665.2	$ 585.8
Translation gain	52.8	17.7
Plan assets at fair market value - end of year	756.7	665.2
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	123.7
Gain on assets sold	0.3
Change in fair value of assets	0.7
Net purchases and sales	8.2
Translation gain	12.4
Plan assets at fair market value - end of year	$ 145.3	$ 123.7