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Risk Management Activities and Derivative Transactions Derivatives Under FTP (Details) - USD ($) $ in Millions | 6 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2022 | Sep. 30, 2021
Derivative |  |
Forward Contract Derivative Asset, at Fair Value | $ 2 | $ 2
Natural Gas Contract Derivatives |  |
Derivative |  |
Fair value | 202 | 247
Commodity Contract under FHP |  |
Derivative |  |
Fair value | 52 | 0
Amount recognized for unrealized gains (losses) | 52 | 0
Fair Value, Inputs, Level 2 |  |
Derivative |  |
Forward Contract Derivative Asset, at Fair Value | 2 | $ 2
Fair Value, Inputs, Level 2 | Commodity Contract under FHP |  |
Derivative |  |
Fair value | $ 52 |

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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=123594938&loc=d3e13433-108611 + Details
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- Definition The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585 + Details
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