Employee Benefit Plans - Amounts Recognized in Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accounts payable and accrued liabilities	$ (1)
Other liabilities	(2)	$ (3)
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Other assets	35	21
Accounts payable and accrued liabilities	(1)	(2)
Other liabilities	(38)	(46)
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accounts payable and accrued liabilities	(3)	(3)
Other liabilities	(22)	(24)
Postretirement Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accounts payable and accrued liabilities	(1)	(1)
Other liabilities	$ (18)	$ (19)