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Asset Retirement Obligations (Details) - USD ($) $ in Millions |  |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Jun. 30, 2016 | May 30, 2016 | Jun. 30, 2017 | Dec. 31, 2017 | Dec. 31, 2016
Asset Retirement Obligations [Line Items] |  |  |  |  |
Nuclear plant decommissioning trusts |  |  |  | $ 2,678 | $ 2,514
Changes to the asset retirement obligations |  |  |  |  |
Beginning Balance |  |  |  | 1,482 | 1,410
Changes in timing of estimated cash flows (1) |  |  |  | 944 |
Liabilities settled |  |  |  | (12) | (27)
Accretion |  |  |  | 101 | 95
Liabilities Incurred |  |  |  | 0 | 4
Ending Balance |  |  |  | 2,515 | 1,482
FES |  |  |  |  |
Asset Retirement Obligations [Line Items] |  |  |  |  |
Nuclear plant decommissioning trusts |  |  |  | 1,856 | 1,552
Changes to the asset retirement obligations |  |  |  |  |
Beginning Balance |  |  |  | 901 | 831
Changes in timing of estimated cash flows (1) |  |  |  | 944 |
Liabilities settled |  |  |  | (11) | (18)
Accretion |  |  |  | 62 | 56
Liabilities Incurred |  |  |  | 49 | 32
Ending Balance |  |  |  | 1,945 | 901
FES | Beaver Valley, Davis-Besse and Perry Nuclear Generating Stations |  |  |  |  |
Changes to the asset retirement obligations |  |  |  |  |
Beginning Balance |  |  |  | 713 |
Ending Balance |  |  |  | $ 1,758 | 713
FES | Beaver Valley Unit 2 |  |  |  |  |
Changes to the asset retirement obligations |  |  |  |  |
Asset retirement obligations transfers |  |  | $ 73 |  |
NG | Perry Power Plant Unit 1 |  |  |  |  |
Changes to the asset retirement obligations |  |  |  |  |
Asset retirement obligations transfers |  |  |  |  | $ 28
Plant ownership percentage | 100.00% | 100.00% |  |  |

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- Definition Asset Retirement Obligations. + References No definition available. + Details
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- Definition The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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- Definition Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848 + Details
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- Definition Amount of asset retirement obligations incurred during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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- Definition Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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- Definition Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(4) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 35 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6392603&loc=d3e7123-110846 + Details
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- Definition Decommission fund to pay for the costs of decontaminating and decommissioning of facilities through collection of revenues derived from utility assessments and government appropriations. Decommission fund investment for the process whereby a power station, at the end of its economic life, is taken permanently out of service and its site made available for other purposes. In the case of a nuclear station this comprises three different states of clearance. Immediately after the final closure, radioactive material such as nuclear fuel and operational waste is removed and the buildings surrounding the reactor shield are dismantled and finally the reactor itself is dismantled. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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