Securities (Tables)

12 Months Ended

Sep. 30, 2020

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. The majority of the MBS and investment securities portfolios are composed of securities issued by GSEs.

	September 30, 2020
			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
	(Dollars in thousands)
MBS	$	1,149,922	$	31,212	$	331	$	1,180,803
GSE debentures	369,967		414		41		370,340
Municipal bonds	9,716		91		—		9,807
	$	1,529,605	$	31,717	$	372	$	1,560,950

	September 30, 2019
			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
	(Dollars in thousands)
MBS	$	923,256	$	15,571	$	2,340	$	936,487
GSE debentures	249,828		304		178		249,954
Municipal bonds	18,371		52		1		18,422
	$	1,191,455	$	15,927	$	2,519	$	1,204,863

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.

	September 30, 2020
	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	$	207,071	$	330	$	118	$	1
GSE debentures	74,959		41		—		—
Municipal bonds	—		—		—		—
	$	282,030	$	371	$	118	$	1

	September 30, 2019
	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	$	111,368	$	126	$	199,442	$	2,214
GSE debentures	—		—		74,812		178
Municipal bonds	1,755		1		—		—
	$	113,123	$	127	$	274,254	$	2,392

Schedule Of Contractual Maturities

The amortized cost and estimated fair value of AFS debt securities as of September 30, 2020, 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 prepayment penalty. For this reason, MBS are not included in the maturity categories.

	Amortized		Estimated
	Cost		Fair Value
	(Dollars in thousands)
One year or less	$	3,987	$	4,009
One year through five years	375,696		376,138
	379,683		380,147
MBS	1,149,922		1,180,803
	$	1,529,605	$	1,560,950

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 Year Ended September 30,
	2020		2019		2018
	(Dollars in thousands)
Taxable	$	4,242	$	6,020	$	4,275
Non-taxable	225		346		395
	$	4,467	$	6,366	$	4,670

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.

	September 30,
	2020		2019
	(Dollars in thousands)
Public unit deposits	$	330,986	$	381,143
FRB of Kansas City	259,851		6,636
Repurchase agreements	—		108,271
	$	590,837	$	496,050