Assets Held For Sale - Disposal Groups, Including Discontinued Operations (Details) - Aquarion - Disposal Group, Held-for-Sale, Not Discontinued Operations - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Restricted Cash	$ 5.8	$ 5.8
Receivables, Net	16.6	14.4
Unbilled Revenues	7.6	11.5
Prepayments and Other Current Assets	24.7	24.6
Total Current Assets Held for Sale	54.7	56.3
Property, Plant and Equipment, Net	1,897.9	1,885.2
Regulatory Assets	49.9	51.2
Goodwill	662.5	662.5
Other Long-Term Assets	14.3	12.2
Total Long-Term Assets Held for Sale	2,624.6	2,611.1
Accounts Payable	14.7	24.2
Other Current Liabilities	28.5	28.4
Total Current Liabilities Held for Sale	43.2	52.6
Regulatory Liabilities	130.7	132.2
Other Long-Term Liabilities	267.0	266.7
Total Long-Term Liabilities Held for Sale	$ 397.7	$ 398.9