Unaudited Quarterly Financial Information - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Schedule Of Quarterly Financial Information Disclosure [Line Items]
Proceeds from the sale of land			$ 39		$ 16
Net discrete tax (benefits) charges related to tax settlements	$ 19		$ 120	$ (25)	$ 1
Operational Restructuring [Member] | Thane, India [Member]
Schedule Of Quarterly Financial Information Disclosure [Line Items]
Proceeds from the sale of land	$ 28	$ 28