RATE REDUCTION BONDS AND VARIABLE INTEREST ENTITIES - Summary of the Impact of Funding on the Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	$ 5,856,600	$ 5,578,300
Regulatory Liabilities	4,021,830	3,930,305
Accrued Interest (included in Other Current Liabilities)	1,108,178	989,053
Rate Reduction Bonds - Current Portion	43,210	43,210
Rate Reduction Bonds - Long-Term Portion	367,282	410,492
Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	403,300	435,700
Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	296,500	322,500
Current Derivative Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	68,400	102,200
Other Long-Term Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	17,500	19,600
PSNH
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	916,500	696,200
Regulatory Liabilities	391,013	391,628
Accrued Interest (included in Other Current Liabilities)	83,046	59,616
Rate Reduction Bonds - Current Portion	43,210	43,210
Rate Reduction Bonds - Long-Term Portion	367,282	410,492
PSNH | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Rate Reduction Bonds - Current Portion	43,200	43,200
Rate Reduction Bonds - Long-Term Portion	367,300	410,500
PSNH | Securitized Stranded Costs
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	403,300	435,700
PSNH | Securitized Stranded Costs | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	403,300	435,700
PSNH | Other Regulatory Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Securitized Stranded Cost (included in Regulatory Assets)	9,000	14,400
PSNH | Other Regulatory Assets | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Regulatory Liabilities	6,700	6,000
Accrued Interest (included in Other Current Liabilities)	2,500	6,900
PSNH | Current Derivative Assets
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	18,200	33,100
PSNH | Current Derivative Assets | VIE
Condensed Balance Sheet Statements, Captions [Line Items]
Restricted Cash	16,600	32,400
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