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v3.19.3

Leases - Narrative (Details) $ in Millions | Sep. 30, 2019 USD ($)
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Lessee, Lease, Description [Line Items] |
Maximum potential loss of lease agreement | $ 15
Operating lease not yet commenced | $ 15
Minimum |
Lessee, Lease, Description [Line Items] |
Operating lease renewal term | 1 year
Renewal term of lease yet to be commenced | 3 years
Maximum |
Lessee, Lease, Description [Line Items] |
Operating lease renewal term | 40 years
Renewal term of lease yet to be commenced | 10 years

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- Definition Lessee, Operating Lease, Lease Not yet Commenced, Amount + References No definition available. + Details
Name: | fe_LesseeOperatingLeaseLeaseNotyetCommencedAmount
Namespace Prefix: | fe_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Lessee, Operating Lease, Residual Value Guarantee, Potential Loss + References No definition available. + Details
Name: | fe_LesseeOperatingLeaseResidualValueGuaranteePotentialLoss
Namespace Prefix: | fe_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_LesseeLeaseDescriptionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Term of lessee's operating lease renewal for lease not yet commenced, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980 + Details
Name: | us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedRenewalTerm1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Definition Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980 + Details
Name: | us-gaap_LesseeOperatingLeaseRenewalTerm
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |