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REVENUES - Narrative (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Apr. 28, 2021
Loss Contingencies [Line Items] |  |  |  |
Revenue | $ 11,890,600 | $ 12,270,200 | $ 9,815,000 |
Loss related to litigation settlement | 0 | (72,041) | 81,274 |
Lease revenue | $ 4,600 | $ 4,000 | $ 4,800 |
Operating Lease, Lease Income, Statement of Income or Comprehensive Income [Extensible Enumeration] | Other Income, Net | Other Income, Net | Other Income, Net |
CL&P |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Loss related to litigation settlement | $ 0 | $ (72,041) | $ 81,274 |
Lease revenue | 700 | 800 | 800 |
NSTAR Electric |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Lease revenue | 2,500 | 2,500 | 3,100 |
Amortization of Revenues Subject to Refund |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Revenue | 4,300 | 72,000 | (78,700) |
Operating Segments | CL&P |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Revenue | 5,077,600 | 5,343,200 | 4,238,900 |
Operating Segments | NSTAR Electric |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Revenue | 4,129,400 | 4,127,300 | 3,541,600 |
Operating Segments | Amortization of Revenues Subject to Refund | CL&P |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Revenue | 4,300 | 72,700 | (76,100) |
Operating Segments | Amortization of Revenues Subject to Refund | NSTAR Electric |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Revenue | $ 0 | $ 0 | 0 |
Unfavorable Regulatory Action |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Loss related to litigation settlement |  |  | 103,600 |
Unfavorable Regulatory Action | CL&P |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Loss contingency, estimate of possible earnings impact, non-compliance with performance standards |  |  |  | $ 28,400
Unfavorable Regulatory Action | Operating Segments | Amortization of Revenues Subject to Refund | CL&P |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Revenue |  |  | 93,400 |
Sales | Unfavorable Regulatory Action |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Loss related to litigation settlement |  |  | 65,000 |
Sales | Unfavorable Regulatory Action | CL&P |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Loss related to litigation settlement |  |  | $ 65,000 |

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