XML 55 R38.htm IDEA: XBRL DOCUMENT v3.21.2

Fair Value Measurements - Level 3 Quantitative Information (Details) - Model - Level 3 - FTRs $ in Millions	6 Months Ended
	Jun. 30, 2021 USD ($) $ / MWh
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value | $	$ 3
Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, RTO Auction Clearing Prices (in $/MWH)	(0.10)
Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, RTO Auction Clearing Prices (in $/MWH)	1.90
Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, RTO Auction Clearing Prices (in $/MWH)	0.90

X

- Definition

Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]

+ References

No definition available.

+ Details

Name:	fe_FairValueInputsAssetsAndLiabilitiesQuantitativeInformationLineItems
Namespace Prefix:	fe_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Fair Value Inputs, RTO Auction Clearing Prices

+ References

No definition available.

+ Details

Name:	fe_FairValueInputsRTOAuctionClearingPrices
Namespace Prefix:	fe_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Fair value measurements with unobservable inputs reconciliation recurring basis asset and liability net value.

+ References

No definition available.

+ Details

Name:	fe_FairValueMeasurementsWithUnobservableInputsReconciliationRecurringBasisAssetAndLiabilityNetValue
Namespace Prefix:	fe_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	us-gaap_ValuationTechniqueAxis=fe_ModelMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=fe_FtrsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_WeightedAverageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: