Employee Benefit Plans - Amounts Recognized in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
U.S. Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	$ 3	$ 12
Balance in accumulated other comprehensive income (loss), pretax	3	12
Foreign Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	52	92
Net prior service credit	(1)	(1)
Balance in accumulated other comprehensive income (loss), pretax	51	91
U. S. Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	(6)	(4)
Net prior service credit	(5)	(7)
Balance in accumulated other comprehensive income (loss), pretax	(11)	(11)
Foreign Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	5	6
Balance in accumulated other comprehensive income (loss), pretax	$ 5	$ 6