Commitments, Guarantees and Contingencies - Potential Collateral Obligations (Details) $ in Millions	3 Months Ended
Mar. 31, 2021 USD ($)
Guarantor Obligations [Line Items]
Guarantor obligations	$ 342
Percent of face amount of debt	100.00%
Curing period	30 days
Upon Further Downgrade
Guarantor Obligations [Line Items]
Guarantor obligations	$ 28
Surety Bond (Collateralized Amount)
Guarantor Obligations [Line Items]
Guarantor obligations	$ 314
Percent of face amount of debt	60.00%
Capped portion of surety bond obligations	$ 39
Utilities and FET
Guarantor Obligations [Line Items]
Guarantor obligations	84
Utilities and FET \| Upon Further Downgrade
Guarantor Obligations [Line Items]
Guarantor obligations	28
Utilities and FET \| Surety Bond (Collateralized Amount)
Guarantor Obligations [Line Items]
Guarantor obligations	56
FirstEnergy
Guarantor Obligations [Line Items]
Guarantor obligations	258
FirstEnergy \| Upon Further Downgrade
Guarantor Obligations [Line Items]
Guarantor obligations	0
FirstEnergy \| Surety Bond (Collateralized Amount)
Guarantor Obligations [Line Items]
Guarantor obligations	$ 258

Guarantor Obligations, Capped Portion of Surety Bond Obligations

No definition available.

Name:	fe_GuarantorObligationsCappedPortionOfSuretyBondObligations
Namespace Prefix:	fe_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Guarantor Obligations, Curing Period

+ References

No definition available.

+ Details

Name:	fe_GuarantorObligationsCuringPeriod
Namespace Prefix:	fe_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Guarantor Obligations, Maximum Contractual Obligations, Percent of Face Amount of Debt

+ References

No definition available.

+ Details

Name:	fe_GuarantorObligationsMaximumContractualObligationsPercentOfFaceAmountOfDebt
Namespace Prefix:	fe_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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

Name:	us-gaap_GuaranteeObligationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=121555522&loc=d3e12069-110248

+ Details

Name:	us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=fe_UponFurtherDowngradeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_SuretyBondMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=fe_RegulatedDistributionandRegulatedTransmissionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=srt_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: