Note 10 - Information by Operating Segment - Net Economic Earnings to Net Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Net Income	$ 204.3	$ 179.2	$ 289.4	$ 270.2
Fair value and timing adjustments	(10.2)	26.6	(15.4)	18.8
Acquisition activities	0.0	0.0	1.9	0.0
Income tax adjustments	2.5	(6.6)	3.4	(4.7)
Net Economic Earnings	$ 196.6	$ 199.2	$ 279.3	$ 284.3