Employee Benefits (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, Net Periodic Benefit Cost (Credit) [Abstract]
Defined Contribution Plan, Cost	$ 3.4	$ 3.0	$ 10.1	$ 9.2
Retirement Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	0.5	0.5	1.5	1.8
Interest cost	1.1	1.0	3.1	2.1
Expected return on plan assets	(0.9)	(1.1)	(2.7)	(4.1)
Amortization of unrecognized net loss	0.4	0.4	1.3	0.4
Settlement charge	0.1	0.5	1.1	2.1
Regulatory asset increase	0.0	(0.6)	0.0	0.9
Net periodic benefit cost	1.2	0.7	4.3	3.2
PBOP
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	0.0	0.0	0.0	0.0
Interest cost	0.3	0.2	0.9	0.6
Expected return on plan assets	(0.6)	(0.4)	(1.8)	(1.3)
Amortization of unrecognized net loss	0.0	0.0	0.0	0.0
Settlement charge	0.0	0.0	0.0	0.0
Regulatory asset increase	0.0	0.0	0.0	0.0
Net periodic benefit cost	(0.3)	$ (0.2)	(0.9)	$ (0.7)
Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Defined Benefit Plan, Plan Assets, Contributions by Employer			3.7
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	$ 1.1		$ 1.1