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REGULATORY ACCOUNTING - Components of Regulatory Liabilities (Details) - USD ($) $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | $ 4,520,500 | $ 4,240,200
Less: Current Portion | 612,931 | 389,430
Total Long-Term Regulatory Liabilities | 3,907,582 | 3,850,781
EDIT due to Tax Cuts and Jobs Act of 2017 |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 2,737,100 | 2,778,600
Cost of Removal |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 676,700 | 624,800
Benefit Costs |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 65,900 | 83,600
Regulatory Tracker Mechanisms |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 484,500 | 366,500
AFUDC - Transmission |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 79,600 | 76,800
CL&P Settlement Agreement and Storm Performance Penalty |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 103,400 | 0
Other Regulatory Liabilities |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 373,300 | 309,900
CL&P |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 1,524,800 | 1,342,100
Less: Current Portion | 311,269 | 137,166
Total Long-Term Regulatory Liabilities | 1,213,469 | 1,204,942
CL&P | EDIT due to Tax Cuts and Jobs Act of 2017 |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 1,001,500 | 1,010,700
CL&P | Cost of Removal |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 117,000 | 98,400
CL&P | Benefit Costs |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 0 | 0
CL&P | Regulatory Tracker Mechanisms |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 208,900 | 148,900
CL&P | AFUDC - Transmission |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 43,600 | 44,600
CL&P | CL&P Settlement Agreement and Storm Performance Penalty |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 103,400 | 0
CL&P | Other Regulatory Liabilities |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 50,400 | 39,500
NSTAR Electric |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 1,767,400 | 1,715,200
Less: Current Portion | 205,771 | 164,761
Total Long-Term Regulatory Liabilities | 1,561,572 | 1,550,390
NSTAR Electric | EDIT due to Tax Cuts and Jobs Act of 2017 |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 1,025,600 | 1,044,000
NSTAR Electric | Cost of Removal |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 384,100 | 363,600
NSTAR Electric | Benefit Costs |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 56,500 | 72,500
NSTAR Electric | Regulatory Tracker Mechanisms |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 180,600 | 139,700
NSTAR Electric | AFUDC - Transmission |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 36,000 | 32,200
NSTAR Electric | CL&P Settlement Agreement and Storm Performance Penalty |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 0 | 0
NSTAR Electric | Other Regulatory Liabilities |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 84,600 | 63,200
PSNH |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 486,200 | 442,000
Less: Current Portion | 96,817 | 58,756
Total Long-Term Regulatory Liabilities | 389,426 | 383,183
PSNH | EDIT due to Tax Cuts and Jobs Act of 2017 |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 363,900 | 371,500
PSNH | Cost of Removal |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 19,000 | 12,900
PSNH | Benefit Costs |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 0 | 0
PSNH | Regulatory Tracker Mechanisms |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 87,500 | 47,800
PSNH | AFUDC - Transmission |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 0 | 0
PSNH | CL&P Settlement Agreement and Storm Performance Penalty |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | 0 | 0
PSNH | Other Regulatory Liabilities |  |
Regulatory Liabilities [Line Items] |  |
Total Regulatory Liabilities | $ 15,800 | $ 9,800

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