Retirement Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Components of net periodic benefit cost:
Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit	$ 21.1	$ 16.9	$ 19.7	$ (4.1)	$ 12.8	$ 18.1
Pension Plan [Member]
Components of net periodic benefit cost:
Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit				13.9	38.8	(23.2)
Foreign Plan [Member] | Pension Plan [Member]
Components of net periodic benefit cost:
Service cost				1.5	1.7	1.6
Interest cost				7.3	7.2	7.5
Expected return on plan assets				(10.2)	(11.6)	(11.1)
Amortization of prior service cost				0.2	0.1	0.0
Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit				17.4	8.8	0.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment				0.0	0.0	0.0
Net periodic benefit (credit) cost				16.2	6.2	(1.9)
United States [Member] | Pension Plan [Member]
Components of net periodic benefit cost:
Service cost				10.7	12.6	12.2
Interest cost				23.5	24.0	24.6
Expected return on plan assets				(25.8)	(29.3)	(28.0)
Amortization of prior service cost				1.6	1.7	1.4
Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit				(3.5)	30.0	23.1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment				0.0	(10.2)	(1.1)
Net periodic benefit (credit) cost				$ 6.5	$ 28.8	$ 32.2