SHORT-TERM AND LONG-TERM DEBT - Summary of Long-Term Debt Issuance and Repayments (Details) - USD ($) $ in Thousands	1 Months Ended					6 Months Ended
	Jul. 31, 2024	Jun. 30, 2024	May 31, 2024	Apr. 30, 2024	Jan. 31, 2024	Jun. 30, 2024	Jun. 30, 2023
Debt Instrument [Line Items]
Repayments of long-term debt						$ (900,000)	$ (853,000)
Senior Notes | Eversource Parent Series DD Senior Notes | Eversource Parent
Debt Instrument [Line Items]
Interest rate, stated percentage (in percent)					5.00%
Issuances					$ 350,000
Senior Notes | Eversource Parent Series EE Senior Notes | Eversource Parent
Debt Instrument [Line Items]
Interest rate, stated percentage (in percent)					5.50%
Issuances					$ 650,000
Senior Notes | Eversource Parent Series FF Senior Notes | Eversource Parent
Debt Instrument [Line Items]
Interest rate, stated percentage (in percent)				5.85%
Issuances				$ 700,000
Senior Notes | Eversource Parent Series GG Senior Notes | Eversource Parent
Debt Instrument [Line Items]
Interest rate, stated percentage (in percent)				5.95%
Issuances				$ 700,000
Senior Notes | Eversource Parent Series X Senior Notes | Eversource Parent
Debt Instrument [Line Items]
Interest rate, stated percentage (in percent)		4.20%				4.20%
Repayments of long-term debt		$ (900,000)
CL&P
Debt Instrument [Line Items]
Repayments of long-term debt						$ 0	$ (400,000)
CL&P | First Mortgage | CL&P 2024 Series A First Mortgage Bonds
Debt Instrument [Line Items]
Interest rate, stated percentage (in percent)					4.65%
Issuances					$ 350,000
PSNH | First Mortgage | PSNH Series X First Mortgage Bonds
Debt Instrument [Line Items]
Interest rate, stated percentage (in percent)				5.35%
Issuances				$ 300,000
NSTAR Electric | Unsecured Debt | NSTAR Electric 2024 Debentures
Debt Instrument [Line Items]
Interest rate, stated percentage (in percent)			5.40%
Issuances			$ 600,000
Yankee Gas | First Mortgage | Yankee Gas Series W First Mortgage Bonds | Subsequent Event
Debt Instrument [Line Items]
Interest rate, stated percentage (in percent)	5.50%
Issuances	$ 90,000
Yankee Gas | First Mortgage | Yankee Gas Series X First Mortgage Bonds | Subsequent Event
Debt Instrument [Line Items]
Interest rate, stated percentage (in percent)	5.74%
Issuances	$ 90,000
NSTAR Gas | First Mortgage | NSTAR Gas Series W First Mortgage Bonds
Debt Instrument [Line Items]
Interest rate, stated percentage (in percent)		5.29%				5.29%
Issuances		$ 160,000
NSTAR Gas | First Mortgage | NSTAR Gas Series X First Mortgage Bonds
Debt Instrument [Line Items]
Interest rate, stated percentage (in percent)		5.48%				5.48%
Issuances		$ 40,000