Retirement Benefits - Schedule of Significant Changes in Level 3 Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of plan assets, beginning of year	$ 47.5	$ 52.3
Payments	(2.6)	(2.0)
Actuarial (gain) loss	8.8	(5.6)	$ 3.7
Interest income	8.8	(0.9)
Cumulative translation adjustments	2.1	(3.9)
Fair value of plan assets, end of year	57.3	47.5	52.3
Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of plan assets, beginning of year	3.6
Fair value of plan assets, end of year	3.7	3.6
Insurance contracts
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of plan assets, beginning of year	3.6
Fair value of plan assets, end of year	3.7	3.6
Insurance contracts | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of plan assets, beginning of year	3.6	4.4
Payments	(0.4)	(0.5)
Actuarial (gain) loss	0.2	(0.1)
Interest income	0.1	0.1
Cumulative translation adjustments	0.2	(0.3)
Fair value of plan assets, end of year	$ 3.7	$ 3.6	$ 4.4