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Commitments, Guarantees and Contingencies - Other Legal Proceedings (Details) - USD ($) | Dec. 31, 2016 | Dec. 06, 2016 | Dec. 05, 2016 | Dec. 31, 2015
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Loss Contingencies [Line Items] |  |  |  |
Nuclear plant decommissioning trusts | $ 2,514,000,000 |  |  | $ 2,282,000,000
Parental support agreement | 3,300,000,000 |  |  |
Nuclear Plant Matters |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Nuclear plant decommissioning trusts | 2,500,000,000 |  |  |
Additions to parental guarantee associated with funding of decommissioning costs | 25,000,000 |  |  |
NG | Nuclear Plant Matters |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Nuclear plant decommissioning trusts | 10,000,000 |  |  |
FES |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Nuclear plant decommissioning trusts | 1,552,000,000 |  |  | $ 1,327,000,000
NG | Parent Support Agreement | FES | Nuclear Plant Matters |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Parental support agreement | 400,000,000 |  |  |
Revolving Credit Facility | Line of Credit |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Maximum amount borrowed under revolving credit facility | 500,000,000 | $ 4,000,000,000 | $ 3,500,000,000.0 |
Revolving Credit Facility | Line of Credit | Nuclear Plant Matters |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Maximum amount borrowed under revolving credit facility | $ 500,000,000 |  |  |
Revolving Credit Facility | Line of Credit | FES |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Maximum amount borrowed under revolving credit facility |  |  | $ 900,000,000 |

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- Definition Parental Guarantee Associated With Funding Of Decommissioning Costs, Additions + References No definition available. + 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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- Definition The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248 + Details
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