SHORT-TERM DEBT - Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Line of Credit Facility [Line Items]
Borrowings Outstanding as of December 31,	$ 1,930,422	$ 1,442,200
Eversource Parent Commercial Paper Program
Line of Credit Facility [Line Items]
Borrowings Outstanding as of December 31,	1,564,575	1,442,200
Commercial Paper | Eversource Parent Commercial Paper Program
Line of Credit Facility [Line Items]
Borrowings Outstanding as of December 31,	1,771,900	1,442,200
Available Borrowing Capacity as of December 31,	$ 228,100	$ 557,800
Weighted-Average Interest Rate as of December 31,	5.60%	4.63%
Commercial Paper | NSTAR Electric
Line of Credit Facility [Line Items]
Borrowings Outstanding as of December 31,	$ 365,800	$ 0
Available Borrowing Capacity as of December 31,	$ 284,200	$ 650,000
Weighted-Average Interest Rate as of December 31,	5.40%	0.00%