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Asset Retirement Obligations (Details) - USD ($) $ in Millions |  | 9 Months Ended |
--- | --- | --- | ---
Jun. 30, 2016 | Sep. 30, 2016 | Dec. 31, 2015
Asset Retirement Obligations [Line Items] |  |  |
Fair value of decommissioning trust assets |  | $ 2,502 | $ 2,282
Changes to the asset retirement obligations |  |  |
Beginning Balance |  | 1,410 |
Liabilities settled |  | (25) |
Liabilities incurred |  | 4 |
Accretion |  | 70 |
Ending Balance |  | 1,459 |
FES |  |  |
Asset Retirement Obligations [Line Items] |  |  |
Fair value of decommissioning trust assets |  | 1,542 | $ 1,327
Changes to the asset retirement obligations |  |  |
Beginning Balance |  | 831 |
Liabilities settled |  | (17) |
Liabilities incurred |  | 32 |
Accretion |  | 41 |
Ending Balance |  | 887 |
FES | Beaver Valley, Davis-Besse and Perry Power Plants |  |  |
Changes to the asset retirement obligations |  |  |
Ending Balance |  | 701 |
NG | Perry Power Plant Unit 1 |  |  |
Changes to the asset retirement obligations |  |  |
ARO transferred |  | $ 28 |
Ownership percentage | 100.00% |  |

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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 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Asset Retirement Obligation -URI http://asc.fasb.org/extlink&oid=6505190 + 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 Carrying amount of an asset that is legally restricted for purposes of settling an asset retirement 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 (b) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + 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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