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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-SubTopic 20
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
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Amortized cost excluding accrued interest, before allowance for credit loss, fee, and loan in process, of financing receivable. Excludes net investment in lease.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
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Amount of unamortized loan commitment, origination, and other costs (fees) on financing receivable recognized as adjustment to yield. Excludes financing receivable covered under loss sharing agreement.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Amount of unamortized purchase premium (discount) on financing receivable. Excludes financing receivable covered under loss sharing agreement.

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Loans Receivable And Allowance For Credit Losses (Summary Of Loans Receivable) (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023
Loans Receivable [Line Items]
Loans receivable, gross	$ 8,043,000		$ 7,923,251
ACL	22,808	$ 23,970	23,035	$ 25,854	$ 24,634	$ 23,759
Deferred loan fees/discounts	31,159		30,336
Premiums/deferred costs	(34,521)		(37,458)
Loans receivable, net	8,023,554		7,907,338
One- to Four-Family Segment [Member]
Loans Receivable [Line Items]
Loans receivable, gross	6,018,486		6,304,670
ACL	3,532	3,562	3,673	4,806	5,060	5,328
One- to Four-Family Segment [Member] \| Originated [Member]
Loans Receivable [Line Items]
Loans receivable, gross	3,828,171		3,941,952
One- to Four-Family Segment [Member] \| Correspondent Purchased [Member]
Loans Receivable [Line Items]
Loans receivable, gross	2,058,749		2,212,587
One- to Four-Family Segment [Member] \| Bulk Purchased [Member]
Loans Receivable [Line Items]
Loans receivable, gross	116,706		127,161
One- to Four-Family Segment [Member] \| Construction [Member]
Loans Receivable [Line Items]
Loans receivable, gross	14,860		22,970
Commercial Segment [Member]
Loans Receivable [Line Items]
Loans receivable, gross	1,911,841		1,508,978
Commercial Segment [Member] \| Construction [Member]
Loans Receivable [Line Items]
Loans receivable, gross	165,760		187,676
Commercial Segment [Member] \| Commercial Real Estate [Member]
Loans Receivable [Line Items]
Loans receivable, gross	1,561,691		1,191,624
ACL	16,598	19,005	17,968	19,662	18,311	17,076
Commercial Segment [Member] \| Commercial and Industrial [Member]
Loans Receivable [Line Items]
Loans receivable, gross	184,390		129,678
ACL	2,441	1,171	1,186	1,134	1,019	1,104
Consumer Segment [Member]
Loans Receivable [Line Items]
Loans receivable, gross	112,673		109,603
ACL	237	$ 232	208	$ 252	$ 244	$ 251
Consumer Segment [Member] \| Home Equity [Member]
Loans Receivable [Line Items]
Loans receivable, gross	103,564		99,988
Consumer Segment [Member] \| Other [Member]
Loans Receivable [Line Items]
Loans receivable, gross	$ 9,109		$ 9,615