LONG-TERM DEBT - Schedule of Issuances and Repayments (Details) - USD ($) $ in Thousands	1 Months Ended									12 Months Ended
	Jan. 31, 2023	Oct. 31, 2022	Sep. 30, 2022	Aug. 31, 2022	Jul. 31, 2022	Jun. 30, 2022	May 31, 2022	Mar. 31, 2022	Feb. 28, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Repayments of debt										$ (1,175,000)	$ (1,142,500)	$ (327,236)
NSTAR Electric
Debt Instrument [Line Items]
Repayments of debt										(400,000)	(250,000)	(95,000)
CL&P
Debt Instrument [Line Items]
Repayments of debt										0	(120,500)	0
PSNH
Debt Instrument [Line Items]
Repayments of debt										0	(282,000)	0
CL&P 2023 Series A First Mortgage Bonds | Mortgage Bonds | CL&P | Subsequent Event
Debt Instrument [Line Items]
Interest rate	5.25%
Issuance	$ 500,000
CL&P 2013 Series A First Mortgage Bonds | Mortgage Bonds | CL&P | Subsequent Event
Debt Instrument [Line Items]
Interest rate	2.50%
Repayments of debt	$ (400,000)
NSTAR Electric 2022 Debentures | Debentures | NSTAR Electric
Debt Instrument [Line Items]
Interest rate							4.55%
Issuance							$ 450,000
NSTAR Electric 2022 Debentures | Debentures | NSTAR Electric
Debt Instrument [Line Items]
Interest rate			4.95%
Issuance			$ 400,000
NSTAR Electric 2012 Debentures | Debentures | NSTAR Electric
Debt Instrument [Line Items]
Interest rate		2.375%
Repayments of debt		$ (400,000)
PSNH Series W First Mortgage Bonds | Mortgage Bonds | PSNH | Subsequent Event
Debt Instrument [Line Items]
Interest rate	5.15%
Issuance	$ 300,000
Yankee Gas Series B First Mortgage Bonds | First Mortgage Bonds | Yankee Gas Services Company
Debt Instrument [Line Items]
Interest rate								8.48%
Repayments of debt								$ (20,000)
Yankee Gas Series U First Mortgage Bonds | First Mortgage Bonds | Yankee Gas Services Company
Debt Instrument [Line Items]
Interest rate			4.31%
Issuance			$ 100,000
EGMA Series C First Mortgage Bonds | First Mortgage Bonds | EGMA
Debt Instrument [Line Items]
Interest rate						4.70%
Issuance						$ 100,000
NSTAR Gas Series V First Mortgage Bonds | First Mortgage Bonds | NSTAR Gas
Debt Instrument [Line Items]
Interest rate					4.40%
Issuance					$ 125,000
Aquarion Water Company of New Hampshire General Mortgage Bonds | General Mortgage Bonds (GMB) | Aquarion Water Company
Debt Instrument [Line Items]
Interest rate					4.45%
Repayments of debt					$ (5,000)
Aquarion Water Company of Connecticut Senior Notes | Senior Notes | Aquarion Water Company
Debt Instrument [Line Items]
Interest rate				4.69%
Issuance				$ 70,000
Eversource
Debt Instrument [Line Items]
Repayments of debt										$ (750,000)	$ (450,000)	$ 0
Eversource | Eversource Parent Series V Senior Notes | Senior Notes
Debt Instrument [Line Items]
Interest rate									2.90%
Issuance									$ 650,000
Eversource | Eversource Parent Series W Senior Notes | Senior Notes
Debt Instrument [Line Items]
Interest rate									3.375%
Issuance									$ 650,000
Eversource | Eversource Parent Series X Senior Notes | Senior Notes
Debt Instrument [Line Items]
Interest rate						4.20%
Issuance						$ 900,000
Eversource | Eversource Parent Series Y Senior Notes | Senior Notes
Debt Instrument [Line Items]
Interest rate						4.60%
Issuance						$ 600,000
Eversource | Eversource Parent Series K Senior Notes | Senior Notes
Debt Instrument [Line Items]
Interest rate								2.75%
Repayments of debt								$ (750,000)