Pension and Postretirement Benefit Costs - Schedule of Net Periodic Benefit (Benefit) Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Net periodic pension cost (credit)	$ (10.0)	$ (12.2)	$ (29.4)	$ (36.7)
Defined benefit pension plans
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	0.1	0.1	0.1	0.1
Interest cost on projected benefit obligation	3.6	5.3	18.4	16.0
Expected return on plan assets	(3.1)	(6.0)	(16.3)	(17.9)
Net periodic pension cost (credit)	0.6	(0.6)	2.2	(1.8)
Postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Service cost for benefits earned	0.1	0.2	0.4	0.6
Interest cost on projected benefit obligation	2.6	1.7	7.6	5.2
Expected return on plan assets	(0.1)	(0.2)	(0.4)	(0.6)
Amortization of prior service credit	(13.5)	(13.4)	(40.3)	(40.3)
Net periodic pension cost (credit)	$ (10.9)	$ (11.7)	$ (32.7)	$ (35.1)