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Risk Management Activities and Derivative Transactions Derivatives Under FTP (Details) - USD ($) $ in Millions | Mar. 31, 2020 | Sep. 30, 2019
--- | --- | ---
Derivative |  |
Forward Contract Derivative Asset, at Fair Value | $ 10 | $ 22
Coal Contract |  |
Derivative |  |
Fair value | (7) | (4)
Natural Gas Contract Derivatives |  |
Derivative |  |
Fair value | (49) | (37)
Fair Value, Inputs, Level 2 |  |
Derivative |  |
Forward Contract Derivative Asset, at Fair Value | $ 10 | $ 22

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- Definition Fair value as of the balance sheet date of forward contract derivative assets. + References No definition available. + Details
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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=118260190&loc=d3e13433-108611 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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