Retirement Benefits - Change in Benefit Obligations and Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in plan assets
Prepaid pensions (included in Other long-term assets)	$ 51.1	$ 55.0
Pension Benefits
Change in benefit obligation
Benefit obligation at beginning of year	917.4	912.3
Service cost	5.9	12.9	$ 17.7
Interest cost	37.2	41.9	40.5
Plan participants’ contributions	0.6	0.5
Amendments	0.3	(34.1)
Actuarial loss	29.7	88.0
Currency impact	9.7	(18.5)
Other	(0.4)	(0.5)
Benefits paid	(44.3)	(85.1)
Benefit obligation at end of year	956.1	917.4	912.3
Change in plan assets
Fair value of plan assets at beginning of year	705.1	757.6
Actual return on plan assets	58.6	23.6
Employer contributions	9.8	24.3
Plan participants’ contributions	0.6	0.5
Currency impact	9.0	(15.8)
Benefits paid	(44.3)	(85.1)
Fair value of plan assets at end of year	738.8	705.1	757.6
FUNDED STATUS	(217.3)	(212.3)
Prepaid pensions (included in Other long-term assets)	1.5	1.7
Accrued benefit liability (short-term and long-term)	(218.8)	(214.0)
NET AMOUNT RECOGNIZED IN THE CONSOLIDATED BALANCE SHEET	(217.3)	(212.3)
Amounts recognized in Accumulated other comprehensive loss (income) consist of:
Net actuarial loss	270.1	274.2
Prior service cost (credit)	0.6	0.4
NET AMOUNT RECOGNIZED IN ACCUMULATED OTHER COMPREHENSIVE LOSS	270.7	274.6
Other Benefits
Change in benefit obligation
Benefit obligation at beginning of year	26.2	26.6
Service cost	0.1	0.0	0.1
Interest cost	1.0	1.2	1.0
Plan participants’ contributions	0.0	0.0
Amendments	0.0	0.0
Actuarial loss	1.4	0.2
Currency impact	0.0	0.0
Other	0.0	0.0
Benefits paid	(1.7)	(1.8)
Benefit obligation at end of year	27.0	26.2	$ 26.6
Change in plan assets
Employer contributions	1.7	1.8
Benefits paid	(1.7)	(1.8)
FUNDED STATUS	(27.0)	(26.2)
Accrued benefit liability (short-term and long-term)	(27.0)	(26.2)
NET AMOUNT RECOGNIZED IN THE CONSOLIDATED BALANCE SHEET	(27.0)	(26.2)
Amounts recognized in Accumulated other comprehensive loss (income) consist of:
Net actuarial loss	3.0	1.7
Prior service cost (credit)	(2.3)	(3.3)
NET AMOUNT RECOGNIZED IN ACCUMULATED OTHER COMPREHENSIVE LOSS	$ 0.7	$ (1.6)