Securities (Tables)

3 Months Ended

Dec. 31, 2023

Marketable Securities [Abstract]

Amortized Cost, Estimated Fair Value, And Gross Unrealized Gains And Losses Of AFS Securities

The following tables reflect the amortized cost, estimated fair value, and gross unrealized gains and losses of AFS securities at the dates presented.

	December 31, 2023
			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
	(Dollars in thousands)
MBS	$	503,912	$	19,599	$	291	$	523,220
U.S. Treasury bills	213,700		58		—		213,758
Corporate bonds	4,000		—		516		3,484
	$	721,612	$	19,657	$	807	$	740,462

	September 30, 2023
			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
	(Dollars in thousands)
MBS	$	901,440	$	113	$	819	$	900,734
Government-sponsored enterprise ("GSE") debentures	479,610		—		182		479,428
Corporate bonds	4,000		—		622		3,378
Municipal bonds	942		—		—		942
	$	1,385,992	$	113	$	1,623	$	1,384,482

Schedule Of Estimated Fair Value And Gross Unrealized Losses Of Securities In Continuous Unrealized Loss Position

The following tables summarize the estimated fair value and gross unrealized losses of those AFS securities on which an unrealized loss at the dates presented was reported and the continuous unrealized loss position for less than 12 months and equal to or greater than 12 months as of the dates presented.

	December 31, 2023
	Less Than 12 Months				Equal to or Greater Than 12 Months
	Estimated		Unrealized		Estimated		Unrealized
	Fair Value		Losses		Fair Value		Losses
	(Dollars in thousands)
MBS	$	14,485	$	13	$	24,191	$	278
Corporate bonds	—		—		3,484		516
	$	14,485	$	13	$	27,675	$	794

	September 30, 2023
	Less Than 12 Months				Equal to or Greater Than 12 Months
	Estimated		Unrealized		Estimated		Unrealized
	Fair Value		Losses		Fair Value		Losses
	(Dollars in thousands)
MBS	$	6,179	$	109	$	34,555	$	710
GSE debentures	—		—		24,818		182
Corporate bonds	—		—		3,378		622
	$	6,179	$	109	$	62,751	$	1,514

Schedule Of Contractual Maturities

The amortized cost and estimated fair value of AFS debt securities as of December 31, 2023, by contractual maturity, are shown below.  Actual principal repayments may differ from contractual maturities due to prepayment or early call privileges by the issuer. In the case of MBS, borrowers on the underlying loans generally have the right to prepay their loans without penalty. For this reason, MBS are not included in the maturity categories.

	Amortized		Estimated
	Cost		Fair Value
	(Dollars in thousands)
One year or less	$	213,700	$	213,758
Five years through ten years	4,000		3,484
	217,700		217,242
MBS	503,912		523,220
	$	721,612	$	740,462

Schedule Of Taxable And Non-taxable Components Of Interest Income

The following table presents the taxable and non-taxable components of interest income on investment securities for the periods presented.

	For the Three Months Ended
	December 31,
	2023		2022
	(Dollars in thousands)
Taxable	$	2,526	$	874
Non-taxable	2		7
	$	2,528	$	881

Schedule Of Carrying Value Of Securities Pledged As Collateral

The following table summarizes the carrying value of securities pledged as collateral for the obligations indicated below as of the dates presented.

	December 31, 2023		September 30, 2023
	(Dollars in thousands)
Public unit deposits	$	148,330	$	178,396
Federal Reserve Bank of Kansas City ("FRB of Kansas City") borrowings	124,292		519,195
	$	272,622	$	697,591