Restructuring - Recorded Restructuring Activities (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense	$ (30)	$ 3	$ 47
Cost of Sales [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense	(31)	2	33
Selling and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense	$ 1	$ 1	9
Research and Development Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense			$ 5