Risk Management Activities and Derivative Transactions Collateral (Details) - USD ($) $ in Millions	Mar. 31, 2025	Sep. 30, 2024
Derivative
Amount of letters of credit outstanding	$ 6
Forward Contract Derivative Asset, at Fair Value	16	$ 11
Likely cash collateral obligation increase	22
Derivative Liability, Subject to Master Netting Arrangement, after Offset	862	1,122
Collateralized Securities [Member]
Derivative
Derivative, Collateral, Right to Reclaim Cash	462
Credit Risk
Derivative
Derivative Liability, Subject to Master Netting Arrangement, after Offset	862
Letter of Credit
Derivative
Amount of letters of credit outstanding	571	566
Interest Swap Collateral
Derivative
Amount of letters of credit outstanding	465
Interest rate swap collateral
Derivative
Amount of letters of credit outstanding		535
Fair Value, Inputs, Level 2
Derivative
Forward Contract Derivative Asset, at Fair Value	$ 16	$ 11

Fair value as of the balance sheet date of forward contract derivative assets.

No definition available.

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- Definition

The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

+ References

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-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 4H
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- Definition

Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
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-SubTopic 20
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- Definition

Fair value, after effect of master netting arrangement, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and contract can be net settled by means outside contract or delivery of asset. Includes derivative subject to master netting arrangement not elected or qualified to offset. Excludes derivative not subject to master netting arrangement or similar agreement.

+ References

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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

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-Topic 815
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+ Details

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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- Details

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- Details

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- Details

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- Details

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