SHORT-TERM AND LONG-TERM DEBT - Narrative (Details) - USD ($)	6 Months Ended
	Jun. 30, 2023	Jun. 07, 2023	Dec. 31, 2022
Line of Credit Facility [Line Items]
Long-term debt	$ 21,771,980,000		$ 19,723,994,000
Commercial Paper
Line of Credit Facility [Line Items]
Long-term debt	297,500,000
NSTAR Electric
Line of Credit Facility [Line Items]
Long-term debt	4,346,902,000		4,345,085,000
CL&P
Line of Credit Facility [Line Items]
Notes payable to Eversource parent	151,535,000		0
Long-term debt	4,607,331,000		4,216,488,000
CL&P | Related Party
Line of Credit Facility [Line Items]
Notes payable to Eversource parent	449,000,000
Long-term debt	297,500,000
PSNH
Line of Credit Facility [Line Items]
Notes payable to Eversource parent	226,300,000		173,300,000
Long-term debt	1,134,402,000		1,134,914,000
PSNH | Related Party
Line of Credit Facility [Line Items]
Notes payable to Eversource parent	226,300,000		173,300,000
Line of Credit | CL&P
Line of Credit Facility [Line Items]
Maximum borrowing capacity	375,000,000
Amount outstanding under line of credit	0
Line of Credit | PSNH
Line of Credit Facility [Line Items]
Maximum borrowing capacity	250,000,000
Amount outstanding under line of credit	0
Line of Credit | Yankee Gas
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 350,000,000
Commercial Paper | NSTAR Electric
Line of Credit Facility [Line Items]
Maximum borrowing capacity	650,000,000
Line of Credit
Line of Credit Facility [Line Items]
Amount outstanding under line of credit	0		$ 0
Line of Credit | NSTAR Electric
Line of Credit Facility [Line Items]
Maximum borrowing capacity	650,000,000
Eversource Parent | Commercial Paper
Line of Credit Facility [Line Items]
Maximum borrowing capacity	2,000,000,000
Eversource Parent | Line of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 2,000,000,000
Debt instrument term (in years)	5 years
NSTAR Electric | Line of Credit | NSTAR Electric
Line of Credit Facility [Line Items]
Debt instrument term (in years)	5 years