Stock-Based Compensation (Supplemental Stock Option Information) (Details) - Stock Options [Member] - USD ($) shares in Millions, $ in Millions	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of options granted at the closing market price of common stock on the grant date	100.00%
Amount of stock option vesting per year	one-third
Stock option expiration years from date of grant years	10 years
Share-based compensation arrangement by share-based payment award, number of shares available for grant	11.6
Cash received for stock options exercises	$ 126	$ 40	$ 143
Intrinsic value of options exercised	47	16	53
Tax benefit from exercise of stock options	$ 8	$ 8	$ 7

Amount Of Stock Option Vesting Per Year

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Percentage of options granted at the closing market price of common stock on the grant dat

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Stock option expiration years from date of grants.

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Amount of tax benefit from exercise of option under share-based payment arrangement.

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Amount of cash inflow from exercise of option under share-based payment arrangement.

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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.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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