RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Summary of the Impact of Funding on the Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	$ 5,702,400	$ 5,715,800
Regulatory Liabilities	3,901,106	3,866,251
Accrued Interest (included in Other Current Liabilities)	983,663	830,620
Rate Reduction Bonds - Current Portion	43,210	43,210
Rate Reduction Bonds - Long-Term Portion	410,492	453,702
Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	446,500	478,900
Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	248,000	150,000
Current Derivative Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	76,500	78,200
Other Long-Term Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	19,300	44,700
PSNH
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	728,800	786,400
Regulatory Liabilities	381,294	381,366
Accrued Interest (included in Other Current Liabilities)	69,801	63,005
Rate Reduction Bonds - Current Portion	43,210	43,210
Rate Reduction Bonds - Long-Term Portion	410,492	453,702
PSNH | VIE
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
PSNH | Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	446,500	478,900
PSNH | Securitized Stranded Costs | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	446,500	478,900
PSNH | Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	14,100	15,800
PSNH | Other Regulatory Assets | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Regulatory Liabilities	7,900	5,400
Accrued Interest (included in Other Current Liabilities)	2,800	7,500
PSNH | Current Derivative Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	18,700	31,400
PSNH | Current Derivative Assets | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	18,000	31,100
PSNH | Other Long-Term Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	3,200	3,200
PSNH | Other Long-Term Assets | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	$ 3,200	$ 3,200