Restructuring - Recorded Restructuring Activities (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense	$ 3	$ 47	$ 21
Cost of Sales [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense	2	33	10
Selling and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense	$ 1	9	$ 11
Research and Development Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense		$ 5