Retirement Benefits - Components of Pension and Other Benefit Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	$ 0.0	$ 7.6	$ 0.0
Pension Benefits
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1.0	1.2	2.2
Interest cost	23.8	28.0	34.6
Expected return on plan assets	(36.5)	(33.9)	(30.7)
Amortization of prior service cost (credit)	0.2	0.2	0.2
Amortization of actuarial losses (gains)	10.8	9.8	9.6
Curtailment and settlement losses	0.0	7.5	0.3
Net periodic benefit cost	(0.7)	12.8	16.2
Changes recognized in other comprehensive loss (income), before tax:
Current year net actuarial loss (gain)	(1.4)	28.6	31.5
Current year prior service credit	3.6	0.0	0.0
Amortization of prior service (cost) credit	(0.2)	(0.2)	(0.2)
Amortization of net actuarial (losses) gains	(10.8)	(9.8)	(9.6)
Currency impact	(0.2)	0.1	0.7
Settlement adjustment	0.0	(7.6)	0.0
Curtailment adjustments	0.0	0.1	(0.3)
Total recognized in other comprehensive loss	(9.0)	11.2	22.1
TOTAL RECOGNIZED IN NET PERIODIC PENSION COST AND OTHER COMPREHENSIVE LOSS	(9.7)	24.0	38.3
Other Benefits
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	0.0	0.0	0.1
Interest cost	0.6	0.7	1.1
Expected return on plan assets	0.0	0.0	0.0
Amortization of prior service cost (credit)	0.0	(0.4)	(0.9)
Amortization of actuarial losses (gains)	(0.1)	(0.1)	0.1
Curtailment and settlement losses	0.0	0.0	0.0
Net periodic benefit cost	0.5	0.2	0.4
Changes recognized in other comprehensive loss (income), before tax:
Current year net actuarial loss (gain)	(4.1)	0.1	(2.0)
Current year prior service credit	0.0	0.0	0.0
Amortization of prior service (cost) credit	0.0	0.4	0.9
Amortization of net actuarial (losses) gains	0.1	0.1	(0.1)
Currency impact	0.0	0.0	0.0
Settlement adjustment	0.0	0.0	0.0
Curtailment adjustments	0.0	0.0	0.0
Total recognized in other comprehensive loss	(4.0)	0.6	(1.2)
TOTAL RECOGNIZED IN NET PERIODIC PENSION COST AND OTHER COMPREHENSIVE LOSS	$ (3.5)	$ 0.8	$ (0.8)