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Short-Term Borrowings and Bank Lines of Credit (Details Textuals) |  |  | 12 Months Ended |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Feb. 16, 2017 USD ($) agreement | Dec. 06, 2016 USD ($) distribution_utility | Dec. 31, 2016 USD ($) money_pool | Dec. 31, 2021 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Jan. 31, 2017 USD ($) | Dec. 05, 2016 USD ($) | Dec. 31, 2015 USD ($)
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Number of regulated distribution utilities | distribution_utility |  | 10 |  |  |  |  |  |  |  |
Short-term borrowings |  |  | $ 2,675,000,000 |  |  |  |  |  |  | $ 1,708,000,000
Number of money pools | money_pool |  |  | 2 |  |  |  |  |  |  |
Average interest rate for borrowings |  |  | 2.47% |  |  |  |  |  |  | 2.16%
Subsequent Event |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Maximum amount borrowed under revolving credit facility |  |  |  |  |  |  |  | $ 5,000,000,000 |  |
Term Loan |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Term of revolving credit facility |  | 5 years |  |  |  |  |  |  |  |
Face amount of loan |  | $ 1,200,000,000.0 |  |  |  |  |  |  | $ 1,000,000,000 |
Term Loan | Prime Rate |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Variable rate (percent) |  | 0.50% |  |  |  |  |  |  |  |
Term Loan | LIBOR |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Variable rate (percent) |  | 1.00% |  |  |  |  |  |  |  |
Term Loan | Subsequent Event |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Debt Instrument, Number of Agreements | agreement | 2 |  |  |  |  |  |  |  |  |
Term Loan | Variable Rate Term Loan Due 2016 |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Face amount of loan |  |  |  |  |  |  |  |  | 200,000,000 |
Term Loan | $125M Term Loan | Bank of America N.A. | Subsequent Event |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Term of revolving credit facility | 3 years |  |  |  |  |  |  |  |  |
Face amount of loan | $ 125,000,000 |  |  |  |  |  |  |  |  |
Term Loan | $125M Term Loan | The Bank of Nova Scotia | Subsequent Event |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Term of revolving credit facility | 3 years |  |  |  |  |  |  |  |  |
Face amount of loan | $ 125,000,000 |  |  |  |  |  |  |  |  |
FET |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Maximum amount borrowed under revolving credit facility |  |  | $ 1,000,000,000 |  |  |  |  |  |  |
FES |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Short-term borrowings |  |  | 0 |  |  |  |  |  |  | $ 8,000,000
FES | Affiliates |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Other Short-term Borrowings |  |  | 101,000,000 |  |  |  |  |  |  | $ 0
FES | Subsequent Event |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Maximum amount borrowed under revolving credit facility |  |  |  |  |  |  |  | 500,000,000 |  |
FG | FMBs | $250M FMB's |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Face amount of loan |  |  |  |  |  |  |  |  | 250,000,000 |
NG | FMBs | $450M FMB's |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Face amount of loan |  |  |  |  |  |  |  |  | 450,000,000 |
Line of Credit | Revolving Credit Facility |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Term of revolving credit facility |  | 2 years |  |  |  |  |  |  |  |
Maximum amount borrowed under revolving credit facility |  | $ 4,000,000,000 | 500,000,000 |  |  |  |  |  | 3,500,000,000.0 |
Increase in borrowing capacity |  | 500,000,000 |  |  |  |  |  |  |  |
Cross-default provision for other indebtedness |  | 100,000,000 |  |  |  |  |  |  |  |
Amounts excluded from capitalization ratio |  | $ 2,750,000,000.00 |  |  |  |  |  |  |  |
Line of Credit | Revolving Credit Facility | Minimum |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Consolidated debt to total capitalization ratio (percent) |  | 65.00% |  |  |  |  |  |  |  |
Line of Credit | Revolving Credit Facility | Minimum | Forecast |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Interest coverage ratio (percent) |  |  |  | 2.5 | 2.25 | 2 | 1.75 |  |  |
Line of Credit | Revolving Credit Facility | Maximum |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Consolidated debt to total capitalization ratio (percent) |  | 100.00% |  |  |  |  |  |  |  |
Line of Credit | Revolving Credit Facility | Subsequent Event |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Maximum amount borrowed under revolving credit facility |  |  |  |  |  |  |  | 5,000,000,000 |  |
Line of Credit | Revolving Credit Facility | FET |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Maximum amount borrowed under revolving credit facility |  | $ 1,000,000,000 |  |  |  |  |  |  | 1,000,000,000 |
Line of Credit | Revolving Credit Facility | FET | Minimum |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Consolidated debt to total capitalization ratio (percent) |  | 75.00% |  |  |  |  |  |  |  |
Line of Credit | Revolving Credit Facility | FET | Maximum |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Consolidated debt to total capitalization ratio (percent) |  | 100.00% |  |  |  |  |  |  |  |
Line of Credit | Revolving Credit Facility | FET | Subsequent Event |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Maximum amount borrowed under revolving credit facility |  |  |  |  |  |  |  | 1,000,000,000 |  |
Line of Credit | Revolving Credit Facility | FES and AE Supply |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Maximum amount borrowed under revolving credit facility |  |  |  |  |  |  |  |  | 1,500,000,000.0 |
Amounts excluded from capitalization ratio |  | $ 5,500,000,000.0 |  |  |  |  |  |  |  |
Line of Credit | Revolving Credit Facility | FES |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Maximum amount borrowed under revolving credit facility |  |  |  |  |  |  |  |  | 900,000,000 |
Line of Credit | Revolving Credit Facility | FES | Subsequent Event |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Maximum amount borrowed under revolving credit facility |  |  |  |  |  |  |  | $ 500,000,000 |  |
Line of Credit | Revolving Credit Facility | AE Supply |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Maximum amount borrowed under revolving credit facility |  |  |  |  |  |  |  |  | $ 600,000,000 |
Line of Credit | Revolving Credit Facility | FE and FET | Prime Rate |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Variable rate (percent) |  | 0.50% |  |  |  |  |  |  |  |
Line of Credit | Revolving Credit Facility | FE and FET | LIBOR |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Variable rate (percent) |  | 1.00% |  |  |  |  |  |  |  |
Line of Credit | Secured Debt |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Maximum amount borrowed under revolving credit facility |  |  | 200,000,000 |  |  |  |  |  |  |
Line of Credit | Surety Bond | Little Bull Run |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Maximum amount borrowed under revolving credit facility |  |  | 169,000,000 |  |  |  |  |  |  |
Revolving Credit Facility | Parent and Certain Subsidiaries |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Term of revolving credit facility |  | 5 years |  |  |  |  |  |  |  |
Available for Issuance of Letters of Credit | Minimum |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Cross-default provision for other indebtedness |  |  | $ 100,000,000 |  |  |  |  |  |  |
Money Pool | Maximum |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Term of revolving credit facility |  |  | 364 days |  |  |  |  |  |  |
Money Pool | Regulated Companies |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Average interest rate for borrowings |  |  | 0.69% |  |  |  |  |  |  |
Money Pool | Unregulated Companies |  |  |  |  |  |  |  |  |  |
Short-Term Borrowings and Bank Lines of Credit (Textuals) [Abstract] |  |  |  |  |  |  |  |  |  |
Average interest rate for borrowings |  |  | 2.02% |  |  |  |  |  |  |

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