Pension and Other Post-Retirement Benefits - Components of Net Periodic Cost (Benefit) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1.7	$ 1.5	$ 3.1	$ 2.8
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component	(1.0)	0.4	(2.2)	0.6
Defined Benefit Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1.6	1.4	3.0	2.7
Interest cost	4.2	4.1	8.2	8.3
Expected return on plan assets	(5.4)	(5.3)	(10.8)	(10.7)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0.0	0.0	0.0	0.0
Defined Benefit Plan, Amortization of Gain (Loss)	0.3	0.3	0.5	0.5
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	0.7	1.9	0.9	2.2
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0.0	1.4	0.0	1.4
Retiree Health and Life [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.1	0.1	0.1	0.1
Interest cost	0.1	0.2	0.3	0.4
Expected return on plan assets	0.0	0.0	0.0	0.0
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0.0	(0.1)	(0.1)	(0.2)
Defined Benefit Plan, Amortization of Gain (Loss)	(0.2)	(0.2)	(0.3)	(0.3)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	$ 0.0	$ 0.0	0.0	0.0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			$ 0.0	$ 0.0