Retirement Benefit Plans - Fair Value of U.S. and Puerto Rico Pension Plan Assets (Detail) - U.S. and Puerto Rico [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Plan assets at fair market value	$ 433.6	$ 389.4	$ 374.1
Fair Value Measurements at Reporting Date Using: Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Plan assets at fair market value	1.3	2.7
Fair Value Measurements at Reporting Date Using: Significant Other Observable Inputs (Level 2) [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Plan assets at fair market value	432.3	386.7
Cash and Cash Equivalents [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Plan assets at fair market value	1.3	2.7
Cash and Cash Equivalents [Member] | Fair Value Measurements at Reporting Date Using: Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Plan assets at fair market value	1.3	2.7
Equity Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Plan assets at fair market value	287.1	247.3
Equity Securities [Member] | Fair Value Measurements at Reporting Date Using: Significant Other Observable Inputs (Level 2) [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Plan assets at fair market value	287.1	247.3
Intermediate Fixed Income Debt Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Plan assets at fair market value	145.2	139.4
Intermediate Fixed Income Debt Securities [Member] | Fair Value Measurements at Reporting Date Using: Significant Other Observable Inputs (Level 2) [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Plan assets at fair market value	$ 145.2	$ 139.4