Revenue (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025	Dec. 31, 2025
Revenue from Contract with Customer, Excluding Assessed Tax	$ 351.4	$ 286.9	$ 952.6	$ 758.5
RTO Revenue	41.9	37.1	134.5	113.9
RTO Capacity Revenue	2.6	2.2	7.0	3.3
Revenues	353.2	292.7	958.3	772.4
Contract with Customer, Asset, before Allowance for Credit Loss	182.1		182.1		$ 157.4
Other Revenues [Member]
Other non-606 revenue	1.8	5.8	5.7	13.9
Wholesale Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	9.8	6.4	31.8	20.9
Retail Revenue [Member] \| Utility [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	297.1	241.2	779.3	620.4
Retail Revenue [Member] \| Utility [Member] \| Residential Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	190.9	153.2	495.9	395.6
Retail Revenue [Member] \| Utility [Member] \| Commercial Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	64.6	54.5	173.4	138.3
Retail Revenue [Member] \| Utility [Member] \| Industrial Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	26.1	20.7	67.8	54.5
Retail Revenue [Member] \| Utility [Member] \| Governmental Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	11.7	9.2	30.6	23.4
Retail Revenue [Member] \| Utility [Member] \| Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 3.8	$ 3.6	$ 11.6	$ 8.6