COMMON SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Noncontrolling Interest [Line Items]
Dividends on preferred stock	$ 7,519	$ 7,519	$ 7,519
Noncontrolling interest - preferred stock of subsidiaries	155,568	155,568
CL&P and NSTAR Electric
Noncontrolling Interest [Line Items]
Dividends on preferred stock	$ 7,500	$ 7,500	$ 7,500

As of the reporting date, the carrying amount of noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. The noncontrolling interest holder's ownership (or holders' ownership) may be in the form of preferred shares (regardless of class), preferred partnership units (regardless of class), preferential membership interests, or any other form of preferred equity regardless of investee entity legal form.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 480
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479857/480-10-S50-3

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 480
-SubTopic 10
-Name Accounting Standards Codification
-Section S45
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479887/480-10-S45-3

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 480
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3A
-Subparagraph (24)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480244/480-10-S99-3A

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant