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Organization and Basis of Presentation (Details Textuals) mi in Thousands, MW in Thousands, customer in Millions, $ in Millions | 3 Months Ended | 9 Months Ended | 12 Months Ended |
--- | --- | --- | --- | ---
Sep. 30, 2016 USD ($) transmission_center | Sep. 30, 2015 USD ($) | Sep. 30, 2016 USD ($) customer transmission_center company mi MW | Sep. 30, 2015 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2015 USD ($) | Nov. 04, 2016 USD ($)
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Aggregate amount of capacity | MW |  |  | 17 |  |  |  |  |
Length of transmission lines | mi |  |  | 24 |  |  |  |  |
Number of regional transmission centers | transmission_center | 2 |  | 2 |  |  |  |  |
Capitalized cost of equity | $ 11 | $ 10 | $ 28 | $ 40 |  |  |  |
Capitalized interest | 17 | $ 16 | $ 51 | $ 53 |  |  |  |
Utilization of Accelerated Useful Life |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Reduction to depreciation | $ 21 |  |  |  |  |  | $ 19 |
Accounting Standards Update 2015-03 | Deferred Charges and Other Assets |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Debt issuance costs |  |  |  |  |  |  | (93) |
Accounting Standards Update 2015-03 | Long-Term Debt and Other Long-Term Obligations |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Debt issuance costs |  |  |  |  |  |  | 93 |
Regulated Distribution |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Number of existing utility operating companies | company |  |  | 10 |  |  |  |  |
Number of customers served by utility operating companies | customer |  |  | 6 |  |  |  |  |
FES | Accounting Standards Update 2015-03 | Deferred Charges and Other Assets |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Debt issuance costs |  |  |  |  |  |  | (17) |
FES | Accounting Standards Update 2015-03 | Long-Term Debt and Other Long-Term Obligations |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Debt issuance costs |  |  |  |  |  |  | $ 17 |
FES | CES |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Additional collateral posted or accelerated payments |  |  |  |  |  |  |  | $ 355
Scenario, Forecast | FES | CES |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Inability to extend or refinance debt |  |  |  |  | $ 515 | $ 130 |  |
Minimum |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Strategic review of competitive operations period |  |  | 12 months |  |  |  |  |
Maximum |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Strategic review of competitive operations period |  |  | 18 months |  |  |  |  |

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