Retirement Benefit Plans - Accumulated Other Comprehensive Loss (Details) - Pension Plan [Member] - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Net prior service credit	$ 4.8	$ 6.4
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax	4.8	6.4	$ 8.1
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net prior service credit	3.9	4.0
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax	$ 3.9	$ 4.0	$ 0.5