v3.25.2
REGULATORY ACCOUNTING - Components of Regulatory Assets (Details) - USD ($)
$ in Thousands
Jun. 30, 2025
Dec. 31, 2024
Regulatory Assets [Line Items]    
Total Regulatory Assets $ 6,731,900 $ 7,070,700
Less:  Current Portion 1,823,417 2,189,660
Total Long-Term Regulatory Assets 4,908,519 4,880,974
Storm Costs, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 2,003,000 2,039,400
Regulatory Tracking Mechanisms    
Regulatory Assets [Line Items]    
Total Regulatory Assets 1,450,000 1,781,600
Income Taxes, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 991,500 968,400
Benefit Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 985,800 967,400
Securitized Stranded Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 327,700 349,300
Goodwill-related    
Regulatory Assets [Line Items]    
Total Regulatory Assets 238,800 247,200
Cost of Removal    
Regulatory Assets [Line Items]    
Total Regulatory Assets 232,600 198,400
Asset Retirement Obligations    
Regulatory Assets [Line Items]    
Total Regulatory Assets 156,400 150,200
Derivative Liabilities    
Regulatory Assets [Line Items]    
Total Regulatory Assets 26,300 57,200
Other Regulatory Assets    
Regulatory Assets [Line Items]    
Total Regulatory Assets 319,800 311,600
CL&P    
Regulatory Assets [Line Items]    
Total Regulatory Assets 2,093,400 2,325,500
Less:  Current Portion 408,514 638,529
Total Long-Term Regulatory Assets 1,684,883 1,687,029
CL&P | Storm Costs, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 979,800 971,100
CL&P | Regulatory Tracking Mechanisms    
Regulatory Assets [Line Items]    
Total Regulatory Assets 301,200 507,700
CL&P | Income Taxes, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 530,100 521,000
CL&P | Benefit Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 169,100 168,800
CL&P | Securitized Stranded Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
CL&P | Goodwill-related    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
CL&P | Cost of Removal    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
CL&P | Asset Retirement Obligations    
Regulatory Assets [Line Items]    
Total Regulatory Assets 42,700 41,200
CL&P | Derivative Liabilities    
Regulatory Assets [Line Items]    
Total Regulatory Assets 26,300 57,200
CL&P | Other Regulatory Assets    
Regulatory Assets [Line Items]    
Total Regulatory Assets 44,200 58,500
NSTAR Electric    
Regulatory Assets [Line Items]    
Total Regulatory Assets 2,056,600 2,107,100
Less:  Current Portion 900,764 902,770
Total Long-Term Regulatory Assets 1,155,758 1,204,337
NSTAR Electric | Storm Costs, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 554,000 609,800
NSTAR Electric | Regulatory Tracking Mechanisms    
Regulatory Assets [Line Items]    
Total Regulatory Assets 648,800 650,000
NSTAR Electric | Income Taxes, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 153,900 145,400
NSTAR Electric | Benefit Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 304,500 293,600
NSTAR Electric | Securitized Stranded Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
NSTAR Electric | Goodwill-related    
Regulatory Assets [Line Items]    
Total Regulatory Assets 205,000 212,300
NSTAR Electric | Cost of Removal    
Regulatory Assets [Line Items]    
Total Regulatory Assets 8,300 8,500
NSTAR Electric | Asset Retirement Obligations    
Regulatory Assets [Line Items]    
Total Regulatory Assets 81,400 78,300
NSTAR Electric | Derivative Liabilities    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
NSTAR Electric | Other Regulatory Assets    
Regulatory Assets [Line Items]    
Total Regulatory Assets 100,700 109,200
PSNH    
Regulatory Assets [Line Items]    
Total Regulatory Assets 1,014,100 1,065,700
Less:  Current Portion 125,497 173,267
Total Long-Term Regulatory Assets 888,626 892,411
PSNH | Storm Costs, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 469,200 458,500
PSNH | Regulatory Tracking Mechanisms    
Regulatory Assets [Line Items]    
Total Regulatory Assets 123,800 162,800
PSNH | Income Taxes, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 20,000 20,700
PSNH | Benefit Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 64,800 65,600
PSNH | Securitized Stranded Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 327,700 349,300
PSNH | Goodwill-related    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
PSNH | Cost of Removal    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
PSNH | Asset Retirement Obligations    
Regulatory Assets [Line Items]    
Total Regulatory Assets 5,300 5,100
PSNH | Derivative Liabilities    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
PSNH | Other Regulatory Assets    
Regulatory Assets [Line Items]    
Total Regulatory Assets $ 3,300 $ 3,700