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Derivative Instruments (Details 4) - Not Designated as Hedging Instrument - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015
Outstanding net asset (liability) [Roll Forward] |  |
Outstanding net asset (liability), Beginning Balance | $ (135) | $ (140)
Unrealized loss | (18) | (56)
Purchases | 4 | 12
Settlements | 44 | 49
Outstanding net asset (liability), Ending Balance | (105) | (135)
NUGs |  |
Outstanding net asset (liability) [Roll Forward] |  |
Outstanding net asset (liability), Beginning Balance | (136) | (151)
Unrealized loss | (15) | (47)
Purchases | 0 | 0
Settlements | 44 | 62
Outstanding net asset (liability), Ending Balance | (107) | (136)
Regulated FTRs |  |
Outstanding net asset (liability) [Roll Forward] |  |
Outstanding net asset (liability), Beginning Balance | 1 | 11
Unrealized loss | (3) | (9)
Purchases | 4 | 12
Settlements | 0 | (13)
Outstanding net asset (liability), Ending Balance | $ 2 | $ 1

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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
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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: |