DERIVATIVE INSTRUMENTS - Narrative (Details) - NSTAR Electric $ in Millions |
1 Months Ended | 3 Months Ended | 6 Months Ended | |
|---|---|---|---|---|
Jun. 30, 2018 |
Jun. 30, 2026
USD ($)
MWh
MW
|
Jun. 30, 2026
USD ($)
MWh
MW
|
Dec. 31, 2025
MWh
|
|
| Derivative Instruments and Hedging Activities Disclosures [Line Items] | ||||
| Power purchase agreement | 20 years | |||
| Amount of power to be purchased under capacity-related contract (in MW) | MW | 579 | 579 | ||
| Level 3 | ||||
| Derivative Instruments and Hedging Activities Disclosures [Line Items] | ||||
| Gains from changes in fair value | $ | $ 218.3 | $ 438.8 | ||
| Minimum | Level 3 | ||||
| Derivative Instruments and Hedging Activities Disclosures [Line Items] | ||||
| Energy price | 25.88 | 25.88 | 24.65 | |
| Maximum | Level 3 | ||||
| Derivative Instruments and Hedging Activities Disclosures [Line Items] | ||||
| Energy price | 172.12 | 172.12 | 145.33 | |
| Weighted Average | Level 3 | ||||
| Derivative Instruments and Hedging Activities Disclosures [Line Items] | ||||
| Energy price | 59.56 | 59.56 | 53.44 |