Risk Management Activities and Derivative Transactions Offsetting for Derivative Liabilities (Details) $ in Millions	Jun. 30, 2023 USD ($)	Sep. 30, 2022 USD ($) Bond_issues
Offsetting Liabilities [Line Items]
Number of currency swaps outstanding \| Bond_issues		2
Accounts Receivable, before Allowance for Credit Loss, Current	$ 1,514	$ 1,899
Total derivatives not subject to master netting or similar arrangement	22	152
Gross amounts of recognized liabilities	1,256	1,160
Derivative Liability, Not Subject to Master Netting Arrangement	11	7
Amount of letters of credit outstanding	6
Forward Contract Derivative Asset, at Fair Value	8	4
Interest Rate Contract
Offsetting Liabilities [Line Items]
Gross amounts of recognized liabilities	837	905
Letter of Credit
Offsetting Liabilities [Line Items]
Amount of letters of credit outstanding	595	704
Interest Swap Collateral
Offsetting Liabilities [Line Items]
Amount of letters of credit outstanding	569
Fair Value, Inputs, Level 2
Offsetting Liabilities [Line Items]
Forward Contract Derivative Asset, at Fair Value	$ 8	$ 4

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

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Amount, before allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

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