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Risk Management Activities and Derivative Transactions Derivatives Under FTP (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Sep. 30, 2020
--- | --- | ---
Derivative |  |
Forward Contract Derivative Asset, at Fair Value | $ 11 | $ 13
Natural Gas Contract Derivatives |  |
Derivative |  |
Fair value | 22 | 46
Fair Value, Inputs, Level 2 |  |
Derivative |  |
Forward Contract Derivative Asset, at Fair Value | $ 11 | $ 13

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- Definition Fair value of the assets less the liabilities of a derivative or group of derivatives. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611 + Details
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