Employee Benefit Plans - Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss), Pre-Tax (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
U.S. Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net (gains) losses	$ (9)	$ 7	$ 14
Net changes recognized in Total other comprehensive (income) loss	(9)	7	14
Foreign Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net (gains) losses	(35)	31	(8)
Prior service (credit) cost			(2)
Amortization of prior unrecognized loss	(5)	(3)	(4)
Other		(1)	(27)
Net changes recognized in Total other comprehensive (income) loss	(40)	27	(41)
U. S. Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net (gains) losses	(3)	2	1
Prior service (credit) cost			(11)
Amortization of prior service credit	3	3
Amortization of prior unrecognized loss			4
Other		1
Net changes recognized in Total other comprehensive (income) loss		6	$ (6)
Foreign Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net (gains) losses	(1)	5
Net changes recognized in Total other comprehensive (income) loss	$ (1)	$ 5