Employee Benefit Plans - Amounts Recognized in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss			$ (7)
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	$ 1	$ 6
Balance in accumulated other comprehensive income (loss), pretax	1	6
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	20	40
Balance in accumulated other comprehensive income (loss), pretax	20	40
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	(4)	(4)
Balance in accumulated other comprehensive income (loss), pretax	(4)	(4)
Postretirement Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	2	4
Balance in accumulated other comprehensive income (loss), pretax	$ 2	$ 4