Debt and Financing Arrangements - Long-term Debt (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Feb. 28, 2025
Long-term debt:
Less: debt issuance costs	$ (31)	$ (28)
Gross long-term debt	2,395	2,404
Less: current portion	9	8
Long-term debt	2,386	2,396
Short-term debt:
Other bank borrowings	2	1
Total short-term debt	$ 2	$ 1
Weighted average interest rate on short-term debt outstanding (as percent)	3.70%	5.40%
Term Loan B due in 2031
Long-term debt:
Long-term debt, gross	$ 626	$ 632
Unsecured debt \| 8.25% Notes due 2031
Long-term debt:
Interest rate (as percent)	8.25%
Long-term debt, gross	$ 500	500
Unsecured debt \| 4.875% Notes due in 2026
Long-term debt:
Interest rate (as percent)	4.875%
Long-term debt, gross	$ 0	795
Unsecured debt \| 7.50% Notes due in 2033
Long-term debt:
Interest rate (as percent)	7.50%		7.50%
Long-term debt, gross	$ 795	0
Unsecured debt \| Other bank borrowings and finance lease obligations
Long-term debt:
Long-term debt, gross	$ 5	5
Term loan \| 7.00% Secured Notes due 2028
Long-term debt:
Interest rate (as percent)	7.00%
Long-term debt, gross	$ 500	$ 500

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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