Stock-Based Compensation - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation	$ 32,000,000	$ 31,000,000	$ 34,000,000
Income tax benefit recognized for share-based compensation arrangements	$ 0	$ 0	$ 0
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Unrecognized compensation related to unvested share arrangements	$ 24,000,000
Recognition period for unrecognized compensation cost	1 year 9 months 18 days
Performance shares (PSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation related to unvested share arrangements	$ 11,000,000
Recognition period for unrecognized compensation cost	1 year 10 months 24 days
Performance period	3 years