Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2025	Jun. 30, 2024
Other Income (Expense) [Member]
Significant Accounting Policies [Line Items]
Foreign exchange losses						$ (42)
Investment income (loss)	$ 1				$ 2	16
Other Income (Expense) [Member] | Revaluation of Non-functional Currency [Member]
Significant Accounting Policies [Line Items]
Foreign exchange losses	$ (3)	$ (2)			$ (5)	$ (42)
Other Income (Expense) [Member] | Single Devaluation Action [Member]
Significant Accounting Policies [Line Items]
Foreign exchange losses				$ (33)
BOPREAL Bonds [Member]
Significant Accounting Policies [Line Items]
Foreign exchange losses		(2)
Purchase of bonds to settle foreign payables		$ 8	$ 30
Investment income (loss)			(8)
Proceeds from sale of bonds			$ 22