Stock-Based Compensation - Schedule of Supplemental Information for Incentive Awards (Details) - Incentive Shares Member - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total fair value of shares earned/vested (in shares)	$ 158	$ 158	$ 131
Share award distributed in cash, primarily for tax withholding (in shares)	$ 73	$ 69	$ 58