Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net income (loss)		$ (7.7)	$ 14.0	$ 46.3
Net derivative gains and other costs arising during the period, net of tax expense of $9.5; $1.7; and $0.8, respectively	[1]	26.5	4.2	2.1
Reclassification of (gains) losses into net income (loss), net of tax (expense) benefit of $(0.3); $(1.2); and $5.1, respectively		(11.4)	(0.7)	3.3
Other comprehensive income		15.1	3.5	5.4
Comprehensive income		$ 7.4	$ 17.5	$ 51.7

[1] Other costs include the effects of foreign currency translation adjustments which were immaterial during the periods presented.