Retirement Benefits - Change in Benefit Obligations and Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in plan assets
Fair value of plan assets at beginning of year	$ 738.8
Fair value of plan assets at end of year	670.6	$ 738.8
Prepaid pensions (included in Other long-term assets)	66.1	51.1
Pension Benefits
Change in benefit obligation
Benefit obligation at beginning of year	956.1	917.4
Acquisitions	1.3	0.0
Service cost	3.8	5.9	$ 12.9
Interest cost	34.3	37.2	41.9
Plan participants’ contributions	0.4	0.6
Amendments	3.6	0.3
Actuarial loss/(gain)	(72.4)	29.7
Curtailment gain	(5.7)	0.0
Currency impact	(5.7)	9.7
Other	(0.5)	(0.4)
Benefits paid	(70.9)	(44.3)
Benefit obligation at end of year	844.3	956.1	917.4
Change in plan assets
Fair value of plan assets at beginning of year	738.8	705.1
Acquisitions	1.2	0.0
Actual return on plan assets	(27.5)	58.6
Employer contributions	34.0	9.8
Plan participants’ contributions	0.4	0.6
Currency impact	(5.9)	9.0
Benefits paid	(70.9)	(44.3)
Fair value of plan assets at end of year	670.1	738.8	705.1
FUNDED STATUS	(174.2)	(217.3)
Prepaid pensions (included in Other long-term assets)	8.0	1.5
Accrued benefit liability (short-term and long-term)	(182.2)	(218.8)
NET AMOUNT RECOGNIZED IN THE CONSOLIDATED BALANCE SHEET	(174.2)	(217.3)
Amounts recognized in Accumulated other comprehensive loss (income) consist of:
Net actuarial loss	240.8	270.1
Prior service cost (credit)	4.1	0.6
NET AMOUNT RECOGNIZED IN ACCUMULATED OTHER COMPREHENSIVE LOSS	244.9	270.7
Other Benefits
Change in benefit obligation
Benefit obligation at beginning of year	27.0	26.2
Acquisitions	0.0	0.0
Service cost	0.1	0.1	0.0
Interest cost	1.0	1.0	1.2
Plan participants’ contributions	0.0	0.0
Amendments	0.0	0.0
Actuarial loss/(gain)	(0.5)	1.4
Curtailment gain	0.0	0.0
Currency impact	0.0	0.0
Other	0.0	0.0
Benefits paid	(1.5)	(1.7)
Benefit obligation at end of year	26.1	27.0	26.2
Change in plan assets
Fair value of plan assets at beginning of year	0.0	0.0
Acquisitions	0.0	0.0
Actual return on plan assets	0.0	0.0
Employer contributions	1.5	1.7
Plan participants’ contributions	0.0	0.0
Currency impact	0.0	0.0
Benefits paid	(1.5)	(1.7)
Fair value of plan assets at end of year	0.0	0.0	$ 0.0
FUNDED STATUS	(26.1)	(27.0)
Prepaid pensions (included in Other long-term assets)	0.0	0.0
Accrued benefit liability (short-term and long-term)	(26.1)	(27.0)
NET AMOUNT RECOGNIZED IN THE CONSOLIDATED BALANCE SHEET	(26.1)	(27.0)
Amounts recognized in Accumulated other comprehensive loss (income) consist of:
Net actuarial loss	2.4	3.0
Prior service cost (credit)	(1.3)	(2.3)
NET AMOUNT RECOGNIZED IN ACCUMULATED OTHER COMPREHENSIVE LOSS	$ 1.1	$ 0.7