Share-Based Compensation Summary of SARs Exercised (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Total intrinsic value of SARs exercised	$ 333	$ 148	$ 148
Share Based Compensation Tax Benefit Realized From Exercise Of Stock Appreciation Rights	90	53	52
Total fair value of SARs vested	$ 107	$ 30	$ 24

The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on stock appreciation rights which were exercised during the reporting period under the plan.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration