XML 100 R83.htm IDEA: XBRL DOCUMENT
v3.20.4

FAIR VALUE MEASUREMENTS - Level 3 Quantitative Information (Details) - Level 3 $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2020 USD ($) $ / MWh | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
FTRs |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value | $ | $ 3 | $ 3 | $ 9
NUG contracts |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value | $ | 0 | $ (16) | $ (44)
Model | FTRs |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value | $ | $ 3 |  |
Model | Minimum | FTRs |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value Inputs, RTO Auction Clearing Prices (in $/MWH) | $ / MWh | 400,000 |  |
Model | Maximum | FTRs |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value Inputs, RTO Auction Clearing Prices (in $/MWH) | $ / MWh | 2,200,000 |  |
Model | Weighted Average | FTRs |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value Inputs, RTO Auction Clearing Prices (in $/MWH) | $ / MWh | 1,100,000 |  |

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_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: | us-gaap_DerivativeInstrumentRiskAxis=fe_NonUtilityGenerationContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ValuationTechniqueAxis=fe_ModelMember
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: |