Financial Information by Segment & Geographic Area - Sales of Equity Method Affiliate and Discounting Charges for Certain Notes Receivable (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Net sales	$ 850	$ 854	$ 818	$ 720	$ 723	$ 705	$ 678	$ 611	$ 3,242	$ 2,717	$ 2,411
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Net sales									116	106	101
Unallocated and Other [Member] | Royalties, the Impact of Unearned Revenue, the Removal of 100% of the Sales of an Equity Method Affiliate and Discounting Charges for Certain Notes Receivable [Member]
Segment Reporting Information [Line Items]
Net sales									11	11	13
Unallocated and Other [Member] | Shipping and Handling Costs [Member]
Segment Reporting Information [Line Items]
Net sales									$ 105	$ 95	$ 88