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COMMITMENTS AND CONTINGENCIES - CL&P Comprehensive Settlement Agreement (Details) - USD ($) $ / shares in Units, $ in Thousands |  | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Oct. 01, 2021 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Mar. 31, 2022 | Oct. 27, 2021 | Dec. 31, 2020
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Bill of forgiveness |  | $ 166,418 | $ 521,752 | $ 221,008 |  |  | $ 264,950
Regulatory Liabilities |  | 591,750 | 890,786 |  |  |  |
Loss related to litigation settlement |  | 0 | (72,041) | 81,274 |  |  |
Basis points reduction to return on equity, scenario one | 0.90% |  |  |  |  |  |
Basis points reduction to return on equity, scenario two | 0.45% |  |  |  |  |  |
CL&P |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Bill of forgiveness |  | 12,243 | 20,327 | 74,788 |  |  | $ 99,809
Regulatory Liabilities |  | 102,239 | 336,048 |  |  |  |
Loss related to litigation settlement |  | $ 0 | (72,041) | 81,274 |  |  |
CL&P | Customer Assistance Fund |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Bill of forgiveness |  |  |  |  | $ 10,000 |  |
Unfavorable Regulatory Action |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Loss related to litigation settlement |  |  |  | 103,600 |  |  |
Customer credits and assistance | $ 75,000 |  |  |  |  |  |
Loss related to litigation settlement, net of tax |  |  |  | $ 86,100 |  |  |
Loss contingency, after-tax earnings impact per share (in dollars per share) |  |  |  | $ 0.25 |  |  |
Unfavorable Regulatory Action | Sales |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Loss related to litigation settlement |  |  |  | $ 65,000 |  |  |
Unfavorable Regulatory Action | Oil and Gas, Operation and Maintenance |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Loss related to litigation settlement |  |  |  | 10,000 |  |  |
Unfavorable Regulatory Action | CL&P |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Customer credits |  |  |  |  |  | $ 65,000 |
Customer assistance initiatives |  |  |  |  |  | $ 10,000 |
Regulatory Liabilities |  |  |  | 75,000 |  |  |
Unfavorable Regulatory Action | CL&P | Sales |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Loss related to litigation settlement |  |  |  | $ 65,000 |  |  |
Unfavorable Regulatory Action | CL&P | Oil and Gas, Operation and Maintenance |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |
Loss related to litigation settlement |  |  | $ 10,000 |  |  |  |

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