Share-Based Compensation - Schedule of Performance Shares Vested (Details) - Performance shares - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent payout	0.00%	92.00%	177.00%
Shares vested (in thousands) (in shares)	0	31	48
Total fair value of shares vested	$ 0.0	$ 9.0	$ 13.0