RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Income Statement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed Income Statements, Captions [Line Items]
Interest Expense on RRB Principal (included in Interest Expense)	$ 855,441	$ 678,274	$ 582,334
PSNH
Condensed Income Statements, Captions [Line Items]
Interest Expense on RRB Principal (included in Interest Expense)	72,786	59,548	56,998
Variable Interest Entity, Primary Beneficiary | PSNH | Rate Reduction Bonds
Condensed Income Statements, Captions [Line Items]
Amortization of RRB Principal (included in Amortization of Regulatory (Liabilities)/Assets, Net)	43,200	43,200	43,200
Interest Expense on RRB Principal (included in Interest Expense)	$ 15,700	$ 17,000	$ 18,400