RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	$ 5,578,300	$ 5,715,800
Regulatory Liabilities	3,930,305	3,866,251
Accrued Interest (included in Other Current Liabilities)	989,053	830,620
Rate Reduction Bonds - Current Portion	43,210	43,210
Rate Reduction Bonds - Long-Term Portion	410,492	453,702
Other Long-Term Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	$ 19,600	$ 44,700
Restricted Cash and Cash Equivalents, Statement of Financial Position [Extensible Enumeration]	Other Long-Term Assets	Other Long-Term Assets
Other Current Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash and Cash Equivalents, Statement of Financial Position [Extensible Enumeration]	Prepayments and Other Current Assets	Prepayments and Other Current Assets
Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	$ 435,700	$ 478,900
Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	322,500	150,000
PSNH
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	696,200	786,400
Regulatory Liabilities	391,628	381,366
Accrued Interest (included in Other Current Liabilities)	59,616	63,005
Rate Reduction Bonds - Current Portion	43,210	43,210
Rate Reduction Bonds - Long-Term Portion	410,492	453,702
PSNH | Other Long-Term Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	3,200	3,200
PSNH | Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	435,700	478,900
PSNH | Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	14,400	15,800
Variable Interest Entity, Primary Beneficiary | PSNH
Condensed Balance Sheet Statements, Captions [Line Items]
Rate Reduction Bonds - Current Portion	43,200	43,200
Rate Reduction Bonds - Long-Term Portion	410,500	453,700
Variable Interest Entity, Primary Beneficiary | PSNH | Other Long-Term Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	3,200	3,200
Variable Interest Entity, Primary Beneficiary | PSNH | Other Current Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	32,400	31,100
Variable Interest Entity, Primary Beneficiary | PSNH | Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	435,700	478,900
Variable Interest Entity, Primary Beneficiary | PSNH | Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Regulatory Liabilities	6,000	5,400
Accrued Interest (included in Other Current Liabilities)	$ 6,900	$ 7,500