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Discontinued Operations - Narrative (Details) |  |  |  | 1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | --- | ---
May 03, 2018 | Mar. 16, 2018 USD ($) | Mar. 09, 2018 USD ($) MW | Aug. 31, 2017 Natural_gas_plant MW | Mar. 31, 2018 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Short-term borrowings |  |  |  |  |  | $ 1,250,000,000 | $ 1,000,000,000 | $ 1,250,000,000 |
Interest expense |  |  |  |  |  |  | 1,033,000,000 | 1,116,000,000 | $ 1,005,000,000
Increase in uncertain tax positions |  |  |  |  |  |  | 22,000,000 | 125,000,000 | 2,000,000
Current assets - discontinued operations |  |  |  |  |  | 25,000,000 | 33,000,000 | 25,000,000 |
Purchase Agreement with Subsidiary of LS Power |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Plant generation capacity (in MW's) | MW |  |  |  | 1,615 |  |  |  |  |
AE Supply | Purchase Agreement with Subsidiary of LS Power |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Number of gas generating plants | Natural_gas_plant |  |  |  | 4 |  |  |  |  |
AGC | Purchase Agreement with Subsidiary of LS Power |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Ownership percentage | 59.00% |  |  | 59.00% |  |  |  |  |
Bay Shore Unit 1 | Asset Purchase Agreement with Walleye Energy, LLC |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Plant capacity (in MW's) | MW |  |  | 136 |  |  |  |  |  |
Promissory Notes | FES and FENOC |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Interest expense |  |  |  |  |  |  | 33,000,000 | 24,000,000 |
Promissory Notes | AE Supply | FES and FENOC |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Outstanding borrowings |  | $ 102,000,000 |  |  | $ 102,000,000 |  |  |  |
Revolving Credit Facility | Line of Credit | FES |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Line of credit outstanding |  |  | $ 500,000,000 |  |  |  | 500,000,000 |  |
Loan reserves |  |  |  |  | 500,000,000 |  |  |  |
Money Pool | FES and FENOC |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Amount added to debt |  | 88,000,000 |  |  |  |  |  |  |
Short-term borrowings |  | $ 92,000,000 |  |  |  |  |  |  |
Discontinued Operations, Disposed of by Means Other than Sale | FES and FENOC |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Investments in subsidiaries |  |  |  |  | 0 |  | 0 |  |
Gain on deconsolidation, net of tax |  |  |  |  |  |  | 59,000,000 | 435,000,000 | $ 0
Assumption of benefit obligations retained at FE (including Pension, OPEB and EDCP) |  |  |  |  | (820,000,000) |  | 0 | 820,000,000 |
Expenses from transactions with related parties |  |  |  |  |  |  | 37,000,000 | 42,000,000 |
Worthless stock deduction |  |  |  |  |  |  | 4,800,000,000 |  |
Worthless stock deduction, net of tax |  |  |  |  |  |  | 1,000,000,000.0 |  |
Tax consequence of outside basis difference |  |  |  |  |  |  | 448,000,000 |  |
Affiliated companies | Discontinued Operations, Disposed of by Means Other than Sale | FES | FES and FENOC |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Tax effect of discontinued operation due to tax cuts |  |  |  |  |  |  | 54,000,000 | 60,000,000 |
Increase in uncertain tax positions |  |  |  |  |  |  | 14,000,000 | 27,000,000 |
Services Agreements | Affiliated companies | Discontinued Operations, Disposed of by Means Other than Sale | FES | FES and FENOC |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Amounts of transaction |  |  |  |  |  | $ 112,500,000 | 152,000,000 |  |
Power Purchase Agreements | Affiliated companies | Discontinued Operations, Disposed of by Means Other than Sale | FES | FES and FENOC |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Due from related parties |  |  |  |  |  |  | 10,000,000 |  |
Purchases from related party |  |  |  |  |  |  | 171,000,000 | $ 318,000,000 |
Tax Allocation Agreement | Affiliated companies | Discontinued Operations, Disposed of by Means Other than Sale | FES and FENOC |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Due from related parties |  |  |  |  |  |  | $ 94,000,000 |  |
FE | Promissory Notes | FES and FENOC |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Loan reserves |  |  |  |  | 102,000,000 |  |  |  |
FE | Unregulated Money Pool | FES and FENOC |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |
Loan reserves |  |  |  |  | $ 92,000,000 |  |  |  |

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- Definition Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
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