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COMMITMENTS AND CONTINGENCIES - Environmental Sites and Related Reserves (Details) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Mar. 31, 2023 USD ($) site | Sep. 30, 2022 site | Dec. 31, 2022 USD ($)
Site Contingency [Line Items] |  |  |
Number of Sites | site | 59 | 59 |
Reserve | $ | $ 121.2 |  | $ 122.6
CL&P |  |  |
Site Contingency [Line Items] |  |  |
Number of Sites | site | 13 | 13 |
Reserve | $ | $ 13.6 |  | 13.9
NSTAR Electric |  |  |
Site Contingency [Line Items] |  |  |
Number of Sites | site | 10 | 10 |
Reserve | $ | $ 3.4 |  | 3.4
PSNH |  |  |
Site Contingency [Line Items] |  |  |
Number of Sites | site | 8 | 8 |
Reserve | $ | $ 6.1 |  | $ 6.1

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