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Fair Value Measurements (Details Textuals) - USD ($) $ in Millions | 6 Months Ended |
--- | --- | ---
Jun. 30, 2018 | Dec. 31, 2017
Fair Value of Financial Instruments [Line Items] |  |
Investment excludes receivables, payables and accrued income | $ (12) | $ (11)
Cash balance excluded from available for sale securities | 5 | 11
Investments not required to be disclosed | $ 255 | $ 255
NUG contracts |  |
Fair Value of Financial Instruments [Line Items] |  |
Period of future observable data to determine contract price | 2 years |

X
- Definition Cash receivables payables deferred taxes accrued income balance excluded from available for sale securities. + References No definition available. + Details
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- Definition Derivative, Contract Price, Period of Future Observable Data + References No definition available. + Details
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Namespace Prefix: | fe_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair Value of Financial Instruments. + References No definition available. + Details
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Namespace Prefix: | fe_
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Balance Type: | na
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X
- Definition Investments excludes receivables payables deferred taxes and accrued income. + References No definition available. + Details
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X
- Definition Investments not required to be disclosed. + References No definition available. + Details
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Namespace Prefix: | fe_
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Balance Type: | debit
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X
- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |