Employee Benefit Plans - Amounts Recognized in Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Other liabilities	$ (2)	$ (2)
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Other assets	28	31
Accounts payable and accrued liabilities	(2)	(2)
Other liabilities	(27)	(28)
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accounts payable and accrued liabilities	(2)	(2)
Other liabilities	(10)	(11)
Postretirement Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accounts payable and accrued liabilities	(1)	(1)
Other liabilities	$ (10)	$ (11)