Number Of Electric, Natural Gas And Water Customers

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Number Of Regulated Utilities

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Period Of Accounts Receivable Recoverable Under Financial Or Medical Duress

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[Line Items] for Summary of Accounting Policies [Table]

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Amount of cash and cash equivalent. Cash includes, but is not limited to, currency on hand, demand deposit with financial institution, and account with general characteristic of demand deposit. Cash equivalent includes, but is not limited to, short-term, highly liquid investment that is both readily convertible to known amount of cash and so near maturity that it presents insignificant risk of change in value because of change in interest rate.

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The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.

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Amount of cash restricted as to withdrawal or usage, classified as current. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) $ in Thousands, customer in Millions		6 Months Ended
	Jun. 30, 2026 USD ($)	Jun. 30, 2026 USD ($) customer regulatedUtility	Jun. 30, 2025 USD ($)	Dec. 31, 2025 USD ($)
Summary of Accounting Policies [Line Items]
Number of electric, natural gas and water customers \| customer		4.4
Cash and cash equivalent	$ 1,819,319	$ 1,819,319		$ 135,351
Proceeds from sale of Aquarion		2,334,136	$ 0
Aquarion \| Discontinued Operations, Disposed of by Sale
Summary of Accounting Policies [Line Items]
Proceeds from sale of Aquarion	1,700,000
Energy Relief Fund - Merrimack Valley Programs
Summary of Accounting Policies [Line Items]
Restricted cash, current	7,500	$ 7,500		21,400
CL&P
Summary of Accounting Policies [Line Items]
Period of accounts receivable recoverable under financial or medical duress		180 days
Cash and cash equivalent	$ 500	$ 500		$ 87,600
Yankee Gas
Summary of Accounting Policies [Line Items]
Period of accounts receivable recoverable under financial or medical duress		90 days
Connecticut, Massachusetts and New Hampshire
Summary of Accounting Policies [Line Items]
Number of regulated utilities \| regulatedUtility		8