Information by Operating Segment - Reconciliation of Adjusted Earnings (Loss) to Net Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Segment Reconciliation [Abstract]
Net Income	$ 209.3	$ 204.3	$ 290.6	$ 289.4
Fair value and timing adjustments	6.9	(10.2)	6.6	(15.4)
Acquisition and restructuring activities	0.0	0.0	0.0	1.9
Income tax adjustments	(1.8)	2.5	(1.7)	3.4
Adjusted Earnings	$ 214.4	$ 196.6	$ 295.5	$ 279.3