Income Taxes (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2024	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Bad Debt Reserve, Tax Purpose of Qualified Lender	$ 85.5
Unrecorded Deferred Tax Liability, Bad Debt Reserve for Tax Purposes of Qualified Lender	18.0
Income Tax Expense related to Bank's earning distributions	3.4
Deferred tax asset, net loss on securities transaction		$ 47.0
Deferred tax asset, operating loss	36.2
Deferred tax asset, low income housing partnership	$ 10.0