Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Statement of Comprehensive Income [Abstract]
Net derivative gains (losses) and other costs arising during the period, net of tax expense (benefit)	$ 1.0	$ (0.7)	$ 2.5	$ 1.3
Reclassification of (gains) into net income, net of tax (expense)	$ (0.5)	$ (0.3)	$ (0.8)	$ (1.1)