RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Summary of the Impact of Funding on the Income Statements (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Condensed Income Statements, Captions [Line Items]
Interest Expense on RRB Principal (included in Interest Expense)	$ 222,283	$ 178,174	$ 624,140	$ 491,509
PSNH
Condensed Income Statements, Captions [Line Items]
Amortization of RRB Principal (included in Amortization of Regulatory Assets, Net)	9,963	(7,398)	35,234	(43,449)
Interest Expense on RRB Principal (included in Interest Expense)	19,252	15,030	55,901	43,432
PSNH | VIE | Rate Reduction Bonds
Condensed Income Statements, Captions [Line Items]
Amortization of RRB Principal (included in Amortization of Regulatory Assets, Net)	10,800	10,800	32,400	32,400
Interest Expense on RRB Principal (included in Interest Expense)	$ 3,900	$ 4,200	$ 11,900	$ 12,900