Employee Benefit Plans - Amounts Recognized in Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Noncurrent liabilities	$ (118)	$ (122)
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	10	1
Current liabilities		(1)
Noncurrent liabilities	(4)	(4)
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	21	12
Current liabilities	(1)	(1)
Noncurrent liabilities	(70)	(69)
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	(3)	(3)
Noncurrent liabilities	(26)	(30)
Postretirement Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Current liabilities	(1)	(1)
Noncurrent liabilities	$ (18)	$ (19)