Earnings Per Common Share - Schedule of Earnings Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended
		Dec. 31, 2024	Dec. 31, 2023
Earnings Per Share [Abstract]
Net Income (Loss)		$ 81.3	$ 85.1
Less: Provision for preferred dividends		3.7	3.7
Income allocated to participating securities		0.1	0.1
Net Income Available to Common Shareholders		$ 77.5	$ 81.3
Weighted Average Common Shares Outstanding (in millions)		57.7	53.5
Basic Earnings Per Common Share		$ 1.34	$ 1.52
Dilutive Effect of forward sales of common stock, restricted stock and restricted stock units (in millions)	[1]	0.2	0.1
Weighted Average Diluted Common Shares (in millions)		57.9	53.6
Diluted Earnings Per Common Share		$ 1.34	$ 1.52

[1] * Calculation excludes certain outstanding or potential common shares
   (shown in millions by period at the right) attributable to (1) forward
   sales of common stock, (2) stock units subject to performance or
   market conditions and (3) restricted stock, which could have a dilutive
   effect in the future     0.3       0.2