Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Net derivative (losses) gains and other costs arising during the period, net of tax expense	$ (3.7)	$ 9.5	$ 1.7
Reclassification of (gains) into net income (loss), net of tax (expense)	$ (2.9)	$ (3.8)	$ (0.3)