v3.26.1
REGULATORY ACCOUNTING - Components of Regulatory Assets (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Regulatory Assets [Line Items]    
Total Regulatory Assets $ 7,146,200 $ 7,693,700
Less:  Current Portion 1,905,179 1,975,083
Total Long-Term Regulatory Assets 5,241,018 5,718,646
Storm Costs, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 2,044,200 1,959,300
Regulatory Tracking Mechanisms    
Regulatory Assets [Line Items]    
Total Regulatory Assets 1,516,500 1,573,800
Benefit Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 1,025,700 992,800
Income Taxes, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 866,200 1,044,500
Derivative Contracts    
Regulatory Assets [Line Items]    
Total Regulatory Assets 390,300 753,200
Securitized Stranded Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 284,500 306,100
Cost of Removal    
Regulatory Assets [Line Items]    
Total Regulatory Assets 268,500 262,500
Goodwill-related    
Regulatory Assets [Line Items]    
Total Regulatory Assets 222,000 230,400
Asset Retirement Obligations    
Regulatory Assets [Line Items]    
Total Regulatory Assets 169,200 162,800
Environmental Remediation Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 134,100 136,100
EGMA Acquisition and Integration Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 82,300 82,300
Other Regulatory Assets    
Regulatory Assets [Line Items]    
Total Regulatory Assets 142,700 189,900
CL&P    
Regulatory Assets [Line Items]    
Total Regulatory Assets 1,991,000 1,981,400
Less:  Current Portion 254,519 265,175
Total Long-Term Regulatory Assets 1,736,547 1,716,212
CL&P | Storm Costs, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 996,900 991,300
CL&P | Regulatory Tracking Mechanisms    
Regulatory Assets [Line Items]    
Total Regulatory Assets 192,700 206,500
CL&P | Benefit Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 185,100 173,700
CL&P | Income Taxes, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 551,400 546,100
CL&P | Derivative Contracts    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 100
CL&P | Securitized Stranded Costs    
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 | Goodwill-related    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
CL&P | Asset Retirement Obligations    
Regulatory Assets [Line Items]    
Total Regulatory Assets 45,700 44,200
CL&P | Environmental Remediation Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
CL&P | EGMA Acquisition and Integration Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
CL&P | Other Regulatory Assets    
Regulatory Assets [Line Items]    
Total Regulatory Assets 19,200 19,500
NSTAR Electric    
Regulatory Assets [Line Items]    
Total Regulatory Assets 2,599,400 2,802,300
Less:  Current Portion 1,056,092 978,754
Total Long-Term Regulatory Assets 1,543,297 1,823,522
NSTAR Electric | Storm Costs, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 575,900 499,600
NSTAR Electric | Regulatory Tracking Mechanisms    
Regulatory Assets [Line Items]    
Total Regulatory Assets 792,900 705,600
NSTAR Electric | Benefit Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 308,300 300,000
NSTAR Electric | Income Taxes, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 170,900 161,500
NSTAR Electric | Derivative Contracts    
Regulatory Assets [Line Items]    
Total Regulatory Assets 390,300 753,100
NSTAR Electric | Securitized Stranded Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
NSTAR Electric | Cost of Removal    
Regulatory Assets [Line Items]    
Total Regulatory Assets 8,000 8,100
NSTAR Electric | Goodwill-related    
Regulatory Assets [Line Items]    
Total Regulatory Assets 190,600 197,800
NSTAR Electric | Asset Retirement Obligations    
Regulatory Assets [Line Items]    
Total Regulatory Assets 87,600 84,600
NSTAR Electric | Environmental Remediation Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
NSTAR Electric | EGMA Acquisition and Integration Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
NSTAR Electric | Other Regulatory Assets    
Regulatory Assets [Line Items]    
Total Regulatory Assets 74,900 92,000
PSNH    
Regulatory Assets [Line Items]    
Total Regulatory Assets 963,600 961,100
Less:  Current Portion 142,236 119,871
Total Long-Term Regulatory Assets 821,386 841,203
PSNH | Storm Costs, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 471,400 468,400
PSNH | Regulatory Tracking Mechanisms    
Regulatory Assets [Line Items]    
Total Regulatory Assets 112,800 93,200
PSNH | Benefit Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 64,700 61,700
PSNH | Income Taxes, Net    
Regulatory Assets [Line Items]    
Total Regulatory Assets 22,100 23,300
PSNH | Derivative Contracts    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
PSNH | Securitized Stranded Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 284,500 306,100
PSNH | Cost of Removal    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
PSNH | Goodwill-related    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
PSNH | Asset Retirement Obligations    
Regulatory Assets [Line Items]    
Total Regulatory Assets 5,600 5,400
PSNH | Environmental Remediation Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
PSNH | EGMA Acquisition and Integration Costs    
Regulatory Assets [Line Items]    
Total Regulatory Assets 0 0
PSNH | Other Regulatory Assets    
Regulatory Assets [Line Items]    
Total Regulatory Assets $ 2,500 $ 3,000