Consolidated Statements of Comprehensive Income (Loss) (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Statement of Comprehensive Income [Abstract]
Net derivative gains (losses) and other costs arising during the period, net of tax expense (benefit)	$ 0.8	$ 5.8	$ 0.0	$ 6.2
Reclassification of (gains) into net income (loss), net of tax (expense)	$ (0.8)	$ (0.5)	$ (2.3)	$ (1.5)