Retirement Benefits - Components of Pension and Other Benefit Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 2.2	$ 3.8	$ 5.9
Interest cost	34.6	34.3	37.2
Expected return on plan assets	(30.7)	(33.5)	(34.1)
Amortization of prior service cost (credit)	0.2	0.1	0.1
Amortization of actuarial losses (gains)	9.6	10.5	11.4
Curtailment and settlement losses	0.3	0.0	0.4
Net periodic benefit cost	16.2	15.2	20.9
Changes recognized in other comprehensive loss (income), before tax:
Current year net actuarial loss (gain)	31.5	(15.8)	4.2
Current year prior service credit	0.0	2.0	0.3
Amortization of prior service (cost) credit	(0.2)	(0.1)	(0.1)
Amortization of net actuarial (losses) gains	(9.6)	(10.5)	(11.4)
Currency impact	0.7	(1.3)	3.5
Other adjustments	(0.3)	0.0	(0.4)
Total recognized in other comprehensive loss	22.1	(25.7)	(3.9)
TOTAL RECOGNIZED IN NET PERIODIC PENSION COST AND OTHER COMPREHENSIVE LOSS	38.3	(10.5)	17.0
Other Benefits
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	0.1	0.1	0.1
Interest cost	1.1	1.0	1.0
Expected return on plan assets	0.0	0.0	0.0
Amortization of prior service cost (credit)	(0.9)	(0.8)	(1.0)
Amortization of actuarial losses (gains)	0.1	0.0	0.0
Curtailment and settlement losses	0.0	0.0	0.0
Net periodic benefit cost	0.4	0.3	0.1
Changes recognized in other comprehensive loss (income), before tax:
Current year net actuarial loss (gain)	(2.0)	(0.4)	1.4
Current year prior service credit	0.0	0.0	0.0
Amortization of prior service (cost) credit	0.9	1.0	1.0
Amortization of net actuarial (losses) gains	(0.1)	(0.2)	0.0
Currency impact	0.0	0.0	0.0
Other adjustments	0.0	0.0	0.0
Total recognized in other comprehensive loss	(1.2)	0.4	2.4
TOTAL RECOGNIZED IN NET PERIODIC PENSION COST AND OTHER COMPREHENSIVE LOSS	$ (0.8)	$ 0.7	$ 2.5