XML 17 R53.htm IDEA: XBRL DOCUMENT
v3.19.3

Fair Value Measurements - Level 3 Quantitative Information (Details) - Level 3 $ in Millions | 9 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2019 USD ($) MWh $ / MWh | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
FTRs |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value | $ | $ 3 | $ 9 | $ 3
NUG contracts |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value | $ | (24) | $ (44) | $ (79)
Model | FTRs |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value | $ | 3 |  |
Model | NUG contracts |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value | $ | $ (24) |  |
Model | Minimum | FTRs |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value Inputs, RTO Auction Clearing Prices (in $/MWH) | 0.60 |  |
Model | Minimum | NUG contracts |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value Inputs, Power (in MWH) | MWh | 400 |  |
Fair Value Inputs, Power, Regional Prices (in $/MWH) | 26.20 |  |
Model | Maximum | FTRs |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value Inputs, RTO Auction Clearing Prices (in $/MWH) | 3.60 |  |
Model | Maximum | NUG contracts |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value Inputs, Power (in MWH) | MWh | 553,000 |  |
Fair Value Inputs, Power, Regional Prices (in $/MWH) | 28.30 |  |
Model | Weighted Average | FTRs |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value Inputs, RTO Auction Clearing Prices (in $/MWH) | 1.20 |  |
Model | Weighted Average | NUG contracts |  |  |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |  |  |
Fair Value Inputs, Power (in MWH) | MWh | 115,000 |  |
Fair Value Inputs, Power, Regional Prices (in $/MWH) | 27.20 |  |

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, Energy + References No definition available. + Details
Name: | fe_FairValueInputsEnergy
Namespace Prefix: | fe_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair Value Inputs, Power, Regional Prices + References No definition available. + Details
Name: | fe_FairValueInputsPowerRegionalPrices
Namespace Prefix: | fe_
Data Type: | srt-types:perUnitItemType
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: |