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COMMITMENTS AND CONTINGENCIES - Schedule of Number of Sites and Reserves (Details) - site | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020
Loss Contingencies [Line Items] |  |
Number of Sites | 61 | 63
The Connecticut Light and Power Company |  |
Loss Contingencies [Line Items] |  |
Number of Sites | 14 | 15
NSTAR Electric Company |  |
Loss Contingencies [Line Items] |  |
Number of Sites | 11 | 12
Public Service Company of New Hampshire |  |
Loss Contingencies [Line Items] |  |
Number of Sites | 9 | 9

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- Definition Number of environmental sites by NU Entity in the remediation or long-term monitoring phase + References No definition available. + Details
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- Details
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