Restructuring - Restructuring Activities and Related Reserves (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Restructuring Cost And Reserve [Line Items]
Reserve balance	$ 9	$ 19	$ 10
Charges (credit)	47	21	29
Costs charged against liabilities (assets)	(30)	(5)	(4)
Cash (paid) / received	(21)	(24)	(15)
Foreign currency translation adjustment		(2)	(1)
Reserve balance	5	9	19
Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	5	16	7
Charges (credit)	28	9	18
Cash (paid) / received	(30)	(18)	(8)
Foreign currency translation adjustment		(2)	(1)
Reserve balance	3	5	16
Environmental Remediation [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	2	2	2
Charges (credit)			1
Cash (paid) / received			(1)
Reserve balance	2	2	2
Non-Cash Asset Impairment and Accelerated Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Charges (credit)	23	5	4
Costs charged against liabilities (assets)	(23)	(5)	(4)
Asset Sales [Member]
Restructuring Cost And Reserve [Line Items]
Charges (credit)	(9)		1
Costs charged against liabilities (assets)	(7)
Cash (paid) / received	16		(1)
Other [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	2	1	1
Charges (credit)	5	7	5
Cash (paid) / received	$ (7)	(6)	(5)
Reserve balance		$ 2	$ 1