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Derivative Instruments (Details 4) - Not Designated as Hedging Instrument - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016
Outstanding net asset (liability) [Roll Forward] |  |
Outstanding net asset (liability), Beginning Balance | $ (105) | $ (135)
Unrealized loss | (10) | (18)
Purchases | 3 | 4
Settlements | 36 | 44
Outstanding net asset (liability), Ending Balance | (76) | (105)
NUGs |  |
Outstanding net asset (liability) [Roll Forward] |  |
Outstanding net asset (liability), Beginning Balance | (107) | (136)
Unrealized loss | (9) | (15)
Purchases | 0 | 0
Settlements | 37 | 44
Outstanding net asset (liability), Ending Balance | (79) | (107)
Regulated FTRs |  |
Outstanding net asset (liability) [Roll Forward] |  |
Outstanding net asset (liability), Beginning Balance | 2 | 1
Unrealized loss | (1) | (3)
Purchases | 3 | 4
Settlements | (1) | 0
Outstanding net asset (liability), Ending Balance | $ 3 | $ 2

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- Definition Derivative Instruments Not Designated As Hedging Instruments, Additions + References No definition available. + Details
Name: | fe_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAdditions
Namespace Prefix: | fe_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Settled Contracts. + References No definition available. + Details
Name: | fe_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsSettledContracts
Namespace Prefix: | fe_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Derivative instruments not designated as hedging instruments unrealized gain (loss). + References No definition available. + Details
Name: | fe_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsUnrealizedGainLoss
Namespace Prefix: | fe_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Derivatives not designated as hedging instruments at fair value net. + References No definition available. + Details
Name: | fe_DerivativesNotDesignatedAsHedgingInstrumentsAtFairValueNet
Namespace Prefix: | fe_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Outstanding Net Asset (Liability) [Roll Forward] + References No definition available. + Details
Name: | fe_OutstandingNetAssetLiabilityRollForward
Namespace Prefix: | fe_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=fe_NugsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=fe_RegulatedFtrsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |