COMMITMENTS AND CONTINGENCIES - Non-Cancellable Commitments Under Purchase Commitment Contracts Narrative (Details) $ in Millions	9 Months Ended
Sep. 30, 2022 USD ($) MW
Offshore Wind Project
Unrecorded Unconditional Purchase Obligation [Line Items]
Contract term	20 years
Energy capacity (in MW) \| MW	800
Renewable Energy \| NSTAR Electric
Unrecorded Unconditional Purchase Obligation [Line Items]
Unrecorded unconditional purchase obligation	$ 6,824.9
Renewable Energy \| NSTAR Electric \| Massachusetts Clean Energy 83D Contract
Unrecorded Unconditional Purchase Obligation [Line Items]
Contract term	20 years
Unrecorded unconditional purchase obligation	$ 6,000.0
Renewable Energy \| NSTAR Electric \| Minimum \| Massachusetts Clean Energy 83D Contract
Unrecorded Unconditional Purchase Obligation [Line Items]
Estimated costs	240.0
Renewable Energy \| NSTAR Electric \| Maximum \| Massachusetts Clean Energy 83D Contract
Unrecorded Unconditional Purchase Obligation [Line Items]
Estimated costs	$ 375.0

Contractual Obligation, Term Of Contract

No definition available.

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- Definition

Long-Term Purchase Commitment, Energy Production Capacity

+ References

No definition available.

+ Details

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- Definition

Unrecorded Unconditional Purchase Obligation, Annual Amount

+ References

No definition available.

+ Details

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- Definition

Amount of the unrecorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 440
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123406679&loc=d3e25336-109308

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Term of the unrecognized unconditional purchase obligation, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 440
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=123406679&loc=d3e25336-109308

+ Details

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