Retirement Benefits - Change in Benefit Obligations and Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Benefits
Change in benefit obligation
Benefit obligation at beginning of year	$ 670.8	$ 937.7
Service cost	0.6	0.9	$ 1.0
Interest cost	35.2	28.0	23.8
Plan participants’ contributions	0.0	0.0
Amendments	0.0	0.0
Actuarial loss/(gain)	18.1	(214.2)
Curtailment gain	0.0	0.0
Settlements	0.0	(22.5)
Currency impact	3.2	(10.5)
Other	(0.1)	(0.5)
Benefits paid	(52.9)	(48.1)
Benefit obligation at end of year	674.9	670.8	937.7
Change in plan assets
Fair value of plan assets at beginning of year	515.4	765.6
Actual return on plan assets	50.8	(186.6)
Employer contributions	26.5	19.8
Plan participants’ contributions	0.0	0.0
Settlements	0.0	(22.5)
Currency impact	3.3	(12.8)
Benefits paid	(52.9)	(48.1)
Fair value of plan assets at end of year	543.1	515.4	765.6
FUNDED STATUS	(131.8)	(155.4)
Amounts recognized in the consolidated balance sheet consist of:
Prepaid pensions (included in Other long-term assets)	10.0	6.8
Accrued benefit liability (short-term and long-term)	(141.8)	(162.2)
NET AMOUNT RECOGNIZED IN THE CONSOLIDATED BALANCE SHEET	(131.8)	(155.4)
Amounts recognized in Accumulated other comprehensive loss (income) consist of:
Net actuarial loss (gain)	231.1	244.4
Prior service cost (credit)	6.0	6.3
NET AMOUNT RECOGNIZED IN ACCUMULATED OTHER COMPREHENSIVE LOSS	237.1	250.7
Other Benefits
Change in benefit obligation
Benefit obligation at beginning of year	15.9	18.9
Service cost	0.0	0.0	0.0
Interest cost	0.8	0.5	0.6
Plan participants’ contributions	0.0	0.0
Amendments	0.0	0.0
Actuarial loss/(gain)	0.3	(2.2)
Curtailment gain	0.0	0.0
Settlements	0.0	0.0
Currency impact	0.0	0.0
Other	0.0	0.0
Benefits paid	(0.9)	(1.3)
Benefit obligation at end of year	16.1	15.9	18.9
Change in plan assets
Fair value of plan assets at beginning of year	0.0	0.0
Actual return on plan assets	0.0	0.0
Employer contributions	0.9	1.3
Plan participants’ contributions	0.0	0.0
Settlements	0.0	0.0
Currency impact	0.0	0.0
Benefits paid	(0.9)	(1.3)
Fair value of plan assets at end of year	0.0	0.0	$ 0.0
FUNDED STATUS	(16.1)	(15.9)
Amounts recognized in the consolidated balance sheet consist of:
Prepaid pensions (included in Other long-term assets)	0.0	0.0
Accrued benefit liability (short-term and long-term)	(16.1)	(15.9)
NET AMOUNT RECOGNIZED IN THE CONSOLIDATED BALANCE SHEET	(16.1)	(15.9)
Amounts recognized in Accumulated other comprehensive loss (income) consist of:
Net actuarial loss (gain)	(4.7)	(5.5)
Prior service cost (credit)	0.0	0.0
NET AMOUNT RECOGNIZED IN ACCUMULATED OTHER COMPREHENSIVE LOSS	$ (4.7)	$ (5.5)