Pension and Other Post-Retirement Benefits - Components of Net Periodic Cost (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Components of pension and other post retirement benefit costs
Service cost	$ 6.2	$ 5.4	$ 7.9
Defined Benefit Pension [Member]
Components of pension and other post retirement benefit costs
Service cost	6.1	5.3	7.7
Interest cost	16.4	16.6	10.1
Expected return on plan assets	(21.6)	(21.4)	(15.6)
Settlement accounting adjustment	0.0	1.4	7.1
Amortization of unrecognized prior service credit	0.1	0.0	0.0
Unrecognized net actuarial loss (gain)	1.0	0.9	8.6
Net periodic (benefit) cost	2.0	2.8	17.9
Retiree Health and Life [Member]
Components of pension and other post retirement benefit costs
Service cost	0.1	0.1	0.2
Interest cost	0.7	0.8	0.4
Expected return on plan assets	0.0	0.0	0.0
Settlement accounting adjustment	0.0	0.0	0.0
Amortization of unrecognized prior service credit	(0.2)	(0.3)	(0.2)
Unrecognized net actuarial loss (gain)	(0.5)	(0.5)	(0.3)
Net periodic (benefit) cost	$ 0.1	$ 0.1	$ 0.1