v3.25.2
REGULATORY ACCOUNTING - Components of Regulatory Liabilities (Details) - USD ($)
$ in Thousands
Jun. 30, 2025
Dec. 31, 2024
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities $ 4,911,200 $ 4,664,900
Less:  Current Portion 834,793 632,282
Total Long-Term Regulatory Liabilities 4,076,390 4,032,564
EDIT due to Tax Cuts and Jobs Act of 2017    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 2,422,100 2,442,700
Regulatory Tracking Mechanisms    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 896,800 702,400
Cost of Removal    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 717,100 684,100
Deferred Portion of Non-Service Income Components of Pension, SERP and PBOP    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 468,600 427,100
AFUDC - Transmission    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 166,800 154,800
Benefit Costs    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 58,800 69,300
Other Regulatory Liabilities    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 181,000 184,500
CL&P    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 1,666,200 1,520,000
Less:  Current Portion 237,525 124,122
Total Long-Term Regulatory Liabilities 1,428,712 1,395,883
CL&P | EDIT due to Tax Cuts and Jobs Act of 2017    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 952,600 956,600
CL&P | Regulatory Tracking Mechanisms    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 289,700 180,300
CL&P | Cost of Removal    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 239,600 212,800
CL&P | Deferred Portion of Non-Service Income Components of Pension, SERP and PBOP    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 67,200 61,600
CL&P | AFUDC - Transmission    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 67,900 65,100
CL&P | Benefit Costs    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 5,200 4,500
CL&P | Other Regulatory Liabilities    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 44,000 39,100
NSTAR Electric    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 2,130,600 2,079,400
Less:  Current Portion 480,158 436,312
Total Long-Term Regulatory Liabilities 1,650,390 1,643,079
NSTAR Electric | EDIT due to Tax Cuts and Jobs Act of 2017    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 866,500 877,600
NSTAR Electric | Regulatory Tracking Mechanisms    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 457,200 413,600
NSTAR Electric | Cost of Removal    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 448,900 451,300
NSTAR Electric | Deferred Portion of Non-Service Income Components of Pension, SERP and PBOP    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 232,500 211,600
NSTAR Electric | AFUDC - Transmission    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 98,900 89,700
NSTAR Electric | Benefit Costs    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 12,700 21,400
NSTAR Electric | Other Regulatory Liabilities    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 13,900 14,200
PSNH    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 506,500 516,100
Less:  Current Portion 103,868 121,058
Total Long-Term Regulatory Liabilities 402,644 394,982
PSNH | EDIT due to Tax Cuts and Jobs Act of 2017    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 326,600 330,600
PSNH | Regulatory Tracking Mechanisms    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 93,500 114,400
PSNH | Cost of Removal    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 28,600 20,100
PSNH | Deferred Portion of Non-Service Income Components of Pension, SERP and PBOP    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 45,600 42,600
PSNH | AFUDC - Transmission    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 0 0
PSNH | Benefit Costs    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities 4,200 3,900
PSNH | Other Regulatory Liabilities    
Regulatory Liabilities [Line Items]    
Total Regulatory Liabilities $ 8,000 $ 4,500