Defined Benefit Pension Plans and Other Post-Employment Benefit Plans - Net Period Benefit Costs (income) for Post-retirement Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 3.1	$ 4.3	$ 9.2	$ 12.9
Amortization of net prior service credit	0.1	0.0	0.2	0.1
Net periodic (income) cost	(0.4)	(0.2)	(1.4)	(0.6)
Other employee benefit plans
Defined Benefit Plan Disclosure [Line Items]
Interest cost	0.1	0.3	0.4	0.8
Amortization of net prior service credit	0.0	0.0	(0.2)	(0.2)
Amortization of net actuarial gain	0.0	0.0	(0.1)	(0.1)
Net periodic (income) cost	$ 0.1	$ 0.3	$ 0.1	$ 0.5