Employee Benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Defined Contribution Plan, Cost	$ 3.1	$ 3.1
Retirement Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	0.6	0.7
Interest cost	0.6	0.5
Expected return on plan assets	(1.5)	(1.6)
Amortization of unrecognized net loss	0.0	0.3
Settlement charge	0.7	0.4
Regulatory asset decrease	0.7	0.0
Net periodic benefit cost	1.1	0.3
PBOP
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	0.0	0.0
Interest cost	0.2	0.2
Expected return on plan assets	(0.4)	(0.6)
Amortization of unrecognized net loss	0.0	0.0
Settlement charge	0.0	0.0
Regulatory asset decrease	0.0	0.0
Net periodic benefit cost	(0.2)	$ (0.4)
Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Defined Benefit Plan, Plan Assets, Contributions by Employer	0.8
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	$ 2.2