Stock-based Compensation (Details) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
Sep. 30, 2021 USD ($) Plan $ / shares shares	Sep. 30, 2020 USD ($) $ / shares	Sep. 30, 2019 USD ($) $ / shares
Stock Based Compensation Activity [Line Items]
Shares authorized for issuance under 2021 Plan (in shares) \| shares	55
Shares available for issuance under the 2021 Plan (in shares) \| shares	54
Number of share-based compensation plans \| Plan	4
Compensation cost charged against income from share-based compensation plans	$ 97	$ 66	$ 103
Total income tax benefit recognized for share-based compensation arrangements	24	16	26
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options	12	1	6
Proceeds from the exercise of stock options	$ 178	$ 75	$ 171
Employee Stock Option
Stock Based Compensation Activity [Line Items]
Expiration period for stock options	10 years
Weighted-average grant-date fair value of options granted \| $ / shares	$ 9.36	$ 7.29	$ 5.56
Total intrinsic value of options exercised	$ 94	$ 30	$ 73
Proceeds from the exercise of stock options	178	75	171
Total unrecognized compensation cost related to nonvested share-based compensation arrangements granted	$ 10
Weighted average period over which unrecognized compensation cost is expected to be recognized	1 year 7 months 6 days
Stock Appreciation Rights (SARs)
Stock Based Compensation Activity [Line Items]
Payments towards exercise of SARs granted	$ 3	$ 2	$ 3
Restricted (Nonvested) Stock
Stock Based Compensation Activity [Line Items]
Total unrecognized compensation cost related to nonvested share-based compensation arrangements granted	$ 103
Weighted average period over which unrecognized compensation cost is expected to be recognized	2 years
Performance Shares
Stock Based Compensation Activity [Line Items]
Total unrecognized compensation cost related to nonvested share-based compensation arrangements granted	$ 29
Weighted average period over which unrecognized compensation cost is expected to be recognized	1 year 9 months 18 days
Minimum \| Employee Stock Option
Stock Based Compensation Activity [Line Items]
Vesting period	2 years
Maximum \| Employee Stock Option
Stock Based Compensation Activity [Line Items]
Vesting period	3 years
Maximum \| Restricted (Nonvested) Stock
Stock Based Compensation Activity [Line Items]
Vesting period	3 years

Number of share-based compensation plans.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Aggregate cash paid by the entity during the period to settle equity instruments granted under equity-based payment arrangements.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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