Income Taxes - Provisions for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Current expense (benefit):
Federal	$ (1)	$ 24	$ (48)
State	37	18	7
Foreign	49	50	85
Total current expense	85	92	44
Deferred expense (benefit):
Federal	34	45	168
State	(21)	(17)	48
Foreign	(433)	193	262
Total deferred (benefit) expense	(420)	221	478
Total income tax (benefit) expense	$ (335)	$ 313	$ 522