RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Income Statement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Condensed Income Statements, Captions [Line Items]
Interest Expense on RRB Principal (included in Interest Expense)	$ 1,243,266	$ 1,111,336	$ 855,441
PSNH
Condensed Income Statements, Captions [Line Items]
Interest Expense on RRB Principal (included in Interest Expense)	89,960	77,770	72,786
Variable Interest Entity, Primary Beneficiary | PSNH | Rate Reduction Bonds
Condensed Income Statements, Captions [Line Items]
Amortization of RRB Principal (included in Amortization of Regulatory Assets/(Liabilities), Net)	43,200	43,200	43,200
Interest Expense on RRB Principal (included in Interest Expense)	$ 12,800	$ 14,300	$ 15,700