Financial Information by Segment & Geographic Area - Schedule of Reconciliation of Segment Earnings before Interest and Income Taxes to Income (Loss) before Income Taxes and Equity in Earnings of Affiliated Companies (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Interest Expense	$ (76)	$ (81)	$ (90)
Less: Equity in earnings of affiliated companies, net of tax	7	6	5
Operating Segments [Member]
Segment Reporting Information [Line Items]
Segment EBIT	702	701	607
Less: Equity in earnings of affiliated companies, net of tax	7	6	5
Reconciling Items [Member]
Segment Reporting Information [Line Items]
Segment EBIT	702	701	607
Interest Expense	(76)	(81)	(90)
Unallocated corporate costs	(52)	(68)	(54)
General unallocated income (expense)	28	42	22
Less: Equity in earnings of affiliated companies, net of tax	7	6	5
Income (loss) from operations before income taxes and equity in earnings of affiliated companies	565	529	451
Certain Items [Member]
Segment Reporting Information [Line Items]
Certain items	$ (30)	$ (59)	$ (29)