Consolidated Statements of Comprehensive Income - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income		$ 56.0	$ 66.4	$ (7.7)
Net derivative gains (losses) and other costs arising during the period, net of tax expense (benefit) of $1.6, $(3.7); and $9.5, respectively	[1]	4.6	(10.4)	26.5
Reclassification of (gains) into net income (loss), net of tax (expense) of $(1.4); $(2.9); and $(3.8), respectively		(4.0)	(8.2)	(11.4)
Other comprehensive income (loss)		0.6	(18.6)	15.1
Comprehensive income		$ 56.6	$ 47.8	$ 7.4

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