Fair Value Measurement (Narrative) (Details) - USD ($)	3 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Fair Value Measurement [Abstract]
Obligations to return cash collateral	$ 0	$ 10,000,000
Rights to reclaim cash collateral	36,000,000	4,000,000
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	$ 6,701,000,000	$ 7,596,000,000
APLNG [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	10.00%
Equity Method Investments	$ 1,645,000,000
Fair Value - Equity Method Investments	5,574,000,000
Before-Tax Loss - Equity method investments	$ 688,000,000

Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.

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

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

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Fair value portion of investments in an entity not consolidated. Includes, but is not limited to, investments in an entity that is affiliated with the reporting entity by means of direct or indirect ownership, an entity in which the reporting entity shares control of the entity with another party or group, an entity which the company has significant influence, but does not have control and subsidiaries that are not required to be consolidated and are accounted for using the equity or cost method.

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