Financial Information by Segment & Geographic Area - Schedule of Income (Loss) from Continuing Operations before Income Taxes and Equity in Earnings of Affiliated Companies for Unallocated and Other (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting [Abstract]
Increase (decrease) in general unallocated income expense	$ 11	$ 3