Restructuring, Reserve (Details) - Project Momentum Restructuring - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance	$ 19.6	$ 0.9
Charge to Income	45.8	14.1
Cash	43.5	7.7
Non-Cash	7.4	0.9
Restructuring Reserve, Ending Balance	14.5	6.4
Severance & termination related costs
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance	15.4	0.0
Charge to Income	3.7	5.5
Cash	8.0	0.6
Non-Cash	0.0	0.0
Restructuring Reserve, Ending Balance	11.1	4.9
Accelerated depreciation & asset write-offs
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance	0.0	0.0
Charge to Income	5.7	0.9
Cash	0.0	0.0
Non-Cash	5.7	0.9
Restructuring Reserve, Ending Balance	0.0	0.0
Other restructuring related costs
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance	3.3	0.9
Charge to Income	29.2	7.7
Cash	29.1	7.1
Non-Cash	1.5	0.0
Restructuring Reserve, Ending Balance	1.9	$ 1.5
IT enablement
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance	0.9
Charge to Income	7.2
Cash	6.4
Non-Cash	0.2
Restructuring Reserve, Ending Balance	$ 1.5