Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Revenue from Contract with Customer, Excluding Assessed Tax	$ 225.2	$ 206.4	$ 476.0	$ 430.4
RTO Revenue	39.3	34.2	76.9	62.0
RTO Capacity Revenue	0.8	0.3	1.1	0.4
Revenues	229.9	209.2	484.2	435.6
Contract with Customer, Asset, before Allowance for Credit Loss	130.3		130.3		$ 103.9
Utility [Member]
RTO Revenue	39.2	34.2	76.8	62.0
RTO Capacity Revenue	0.8	0.3	1.1	0.4
Revenues	227.6	206.9	479.7	431.2
Corporate and Other
RTO Revenue	0.1	0.0	0.1	0.0
RTO Capacity Revenue	0.0	0.0	0.0	0.0
Revenues	3.7	3.8	7.4	7.3
Adjustments and Eliminations
RTO Revenue	0.0	0.0	0.0	0.0
RTO Capacity Revenue	0.0	0.0	0.0	0.0
Revenues	(1.4)	(1.5)	(2.9)	(2.9)
Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	2.4	2.5	4.9	4.8
Other non-606 revenue	4.7	2.8	8.2	5.2
Other Revenues [Member] | Utility [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0	0.0
Other non-606 revenue	4.6	2.7	8.1	5.1
Other Revenues [Member] | Corporate and Other
Revenue from Contract with Customer, Excluding Assessed Tax	2.4	2.5	4.9	4.8
Other non-606 revenue	1.2	1.3	2.4	2.5
Other Revenues [Member] | Adjustments and Eliminations
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0	0.0
Other non-606 revenue	(1.1)	(1.2)	(2.3)	(2.4)
Wholesale Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	5.0	2.5	13.9	7.3
Wholesale Revenue [Member] | Utility [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	5.3	2.8	14.5	7.8
Wholesale Revenue [Member] | Corporate and Other
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0	0.0
Wholesale Revenue [Member] | Adjustments and Eliminations
Revenue from Contract with Customer, Excluding Assessed Tax	(0.3)	(0.3)	(0.6)	(0.5)
Retail Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	177.7	166.9	379.2	355.9
Other non-606 revenue		0.0
Retail Revenue [Member] | Residential Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	105.7	101.9	242.4	226.2
Retail Revenue [Member] | Commercial Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	44.0	39.4	83.8	78.6
Retail Revenue [Member] | Industrial Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	18.1	16.0	33.8	32.7
Retail Revenue [Member] | Governmental Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	7.2	6.3	14.2	12.1
Retail Revenue [Member] | Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	2.7	3.3	5.0	6.3
Retail Revenue [Member] | Utility [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	177.7	166.9	379.2	355.9
Other non-606 revenue		0.0
Retail Revenue [Member] | Utility [Member] | Residential Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	105.7	101.9	242.4	226.2
Retail Revenue [Member] | Utility [Member] | Commercial Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	44.0	39.4	83.8	78.6
Retail Revenue [Member] | Utility [Member] | Industrial Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	18.1	16.0	33.8	32.7
Retail Revenue [Member] | Utility [Member] | Governmental Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	7.2	6.3	14.2	12.1
Retail Revenue [Member] | Utility [Member] | Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	2.7	3.3	5.0	6.3
Retail Revenue [Member] | Corporate and Other
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0	0.0
Other non-606 revenue		0.0
Retail Revenue [Member] | Corporate and Other | Residential Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0	0.0
Retail Revenue [Member] | Corporate and Other | Commercial Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0	0.0
Retail Revenue [Member] | Corporate and Other | Industrial Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0	0.0
Retail Revenue [Member] | Corporate and Other | Governmental Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0	0.0
Retail Revenue [Member] | Corporate and Other | Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0	0.0
Retail Revenue [Member] | Adjustments and Eliminations
Revenue from Contract with Customer, Excluding Assessed Tax			0.0	0.0
Other non-606 revenue		0.0
Retail Revenue [Member] | Adjustments and Eliminations | Residential Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	$ 0.0	$ 0.0	0.0	0.0
Retail Revenue [Member] | Adjustments and Eliminations | Commercial Revenue
Revenue from Contract with Customer, Excluding Assessed Tax			0.0	0.0
Retail Revenue [Member] | Adjustments and Eliminations | Industrial Revenue
Revenue from Contract with Customer, Excluding Assessed Tax			0.0	0.0
Retail Revenue [Member] | Adjustments and Eliminations | Governmental Revenue
Revenue from Contract with Customer, Excluding Assessed Tax			0.0	0.0
Retail Revenue [Member] | Adjustments and Eliminations | Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax			$ 0.0	$ 0.0