v3.25.2
FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - USD ($)
$ in Thousands
Jun. 30, 2025
Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Preferred Stock Not Subject to Mandatory Redemption $ 155,568 $ 155,568
Rate Reduction Bonds 302,467 324,072
Carrying Amount    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Preferred Stock Not Subject to Mandatory Redemption 155,600 155,600
Long-Term Debt 28,163,300 26,704,800
Rate Reduction Bonds 345,700 367,300
Fair Value | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Preferred Stock Not Subject to Mandatory Redemption 121,400 123,800
Long-Term Debt 26,766,300 24,791,400
Rate Reduction Bonds 338,100 352,100
CL&P    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Preferred Stock Not Subject to Mandatory Redemption 116,200 116,200
CL&P | Carrying Amount    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Preferred Stock Not Subject to Mandatory Redemption 116,200 116,200
Long-Term Debt 5,508,500 5,111,100
Rate Reduction Bonds 0 0
CL&P | Fair Value | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Preferred Stock Not Subject to Mandatory Redemption 89,800 90,300
Long-Term Debt 5,191,900 4,705,800
Rate Reduction Bonds 0 0
NSTAR Electric    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Preferred Stock Not Subject to Mandatory Redemption 43,000 43,000
NSTAR Electric | Carrying Amount    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Preferred Stock Not Subject to Mandatory Redemption 43,000 43,000
Long-Term Debt 5,888,100 5,094,900
Rate Reduction Bonds 0 0
NSTAR Electric | Fair Value | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Preferred Stock Not Subject to Mandatory Redemption 31,600 33,500
Long-Term Debt 5,637,100 4,759,400
Rate Reduction Bonds 0 0
PSNH    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Rate Reduction Bonds 302,467 324,072
PSNH | Carrying Amount    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Preferred Stock Not Subject to Mandatory Redemption 0 0
Long-Term Debt 2,031,100 1,732,100
Rate Reduction Bonds 345,700 367,300
PSNH | Fair Value | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Preferred Stock Not Subject to Mandatory Redemption 0 0
Long-Term Debt 1,861,700 1,529,700
Rate Reduction Bonds $ 338,100 $ 352,100