Note 3 - Earnings Per Common Share - Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Net Income		$ (1.4)	$ 5.3	$ 227.9	$ 281.6
Provision for preferred dividends		3.7	3.7	11.1	11.1
Income allocated to participating securities		0.0	0.1	0.3	0.5
Net (Loss) Income Available to Common Shareholders		$ (5.1)	$ 1.5	$ 216.5	$ 270.0
Basic (in shares)		52.2	51.6	51.9	51.6
Basic (Loss) Earnings Per Common Share (in dollars per share)		$ (0.10)	$ 0.03	$ 4.17	$ 5.24
Dilutive Effect of Restricted Stock and Restricted Stock Units (in millions)* (in shares)	[1]	0.1	0.1	0.1	0.1
Weighted Average Diluted Common Shares (in millions) (in shares)		52.3	51.7	52.0	51.7
Diluted (Loss) Earnings Per Common Share (in dollars per share)		$ (0.10)	$ 0.03	$ 4.16	$ 5.23
* Calculation excludes certain outstanding common shares (shown in millions by period at the right) attributable to stock units subject to performance or market conditions and restricted stock, which could have a dilutive effect in the future (in shares)		0.1	0.1	0.2	0.1

[1] Calculation excludes certain outstanding common shares (shown in millions by period at the right) attributable to stock units subject to performance or market conditions and restricted stock, which could have a dilutive effect in the future