Employee Benefit Plans - Amounts Recognized in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	$ (1)	$ 3
Balance in accumulated other comprehensive income (loss), pretax	(1)	3
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	49	52
Net prior service credit	(1)	(1)
Balance in accumulated other comprehensive income (loss), pretax	48	51
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	(7)	(6)
Net prior service credit	(2)	(5)
Balance in accumulated other comprehensive income (loss), pretax	(9)	(11)
Postretirement Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	4	5
Balance in accumulated other comprehensive income (loss), pretax	$ 4	$ 5