Share-Based Compensation - Schedule of Performance Shares Vested (Details) - Performance shares - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent payout	177.00%	144.00%	93.00%
Shares vested (in thousands) (in shares)	48	68	31
Vested shares, Total Fair Value	$ 12.5	$ 23.4	$ 7.4