Allowance for Losses on Loans - Schedule of Activity in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Sep. 30, 2025
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	$ 201,950	$ 202,709	$ 199,720	$ 203,753	$ 203,753
Charge-offs	(2,430)	(5,797)	(7,755)	(12,025)
Recoveries	811	356	1,866	1,290
Provision & Transfers	14,500	1,500	21,000	5,750
Ending Allowance	214,831	198,768	214,831	198,768	199,720
Provision (recapture)	14,500	1,500	21,000	5,750
Commercial loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	160,492	151,281	152,134	153,373	153,373
Charge-offs	(1,573)	(5,582)	(6,112)	(10,730)	(11,498)
Recoveries	707	207	1,621	437
Provision & Transfers	18,240	3,468	30,223	6,294
Ending Allowance	177,866	149,374	177,866	149,374	152,134
Provision (recapture)	18,240	3,468	30,223	6,294
Commercial loans \| Multi-family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	25,923	26,556	25,953	25,248	25,248
Charge-offs	0	(373)	(81)	(373)	(555)
Recoveries	0	0	0	0
Provision & Transfers	(277)	623	(226)	1,931
Ending Allowance	25,646	26,806	25,646	26,806	25,953
Provision (recapture)	(277)	623	(226)	1,931
Commercial loans \| Commercial real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	41,503	38,469	41,988	39,210	39,210
Charge-offs	(957)	(5,097)	(957)	(9,652)	(9,652)
Recoveries	685	0	1,340	169
Provision & Transfers	(459)	8,903	(1,599)	12,548
Ending Allowance	40,772	42,275	40,772	42,275	41,988
Provision (recapture)	(459)	8,903	(1,599)	12,548
Commercial loans \| Commercial & industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	68,662	60,147	59,163	58,748	58,748
Charge-offs	(616)	(112)	(5,074)	(705)	(1,291)
Recoveries	16	201	159	243
Provision & Transfers	16,831	(3,463)	30,645	(1,513)
Ending Allowance	84,893	56,773	84,893	56,773	59,163
Provision (recapture)	16,831	(3,463)	30,645	(1,513)
Commercial loans \| Construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	16,712	19,406	18,136	22,267	22,267
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision & Transfers	1,383	(2,293)	(41)	(5,154)
Ending Allowance	18,095	17,113	18,095	17,113	18,136
Provision (recapture)	1,383	(2,293)	(41)	(5,154)
Commercial loans \| Land - acquisition & development
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	7,692	6,703	6,894	7,900	7,900
Charge-offs	0	0	0	0
Recoveries	6	6	122	25
Provision & Transfers	762	(302)	1,444	(1,518)
Ending Allowance	8,460	6,407	8,460	6,407	6,894
Provision (recapture)	762	(302)	1,444	(1,518)
Consumer loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	41,458	51,428	47,586	50,380	50,380
Charge-offs	(857)	(215)	(1,643)	(1,295)	(1,672)
Recoveries	104	149	245	853
Provision & Transfers	(3,740)	(1,968)	(9,223)	(544)
Ending Allowance	36,965	49,394	36,965	49,394	47,586
Provision (recapture)	(3,740)	(1,968)	(9,223)	(544)
Consumer loans \| Construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	302	1,076	610	1,427	1,427
Charge-offs	0	0	0	0
Recoveries	2	2	6	2
Provision & Transfers	(176)	(332)	(488)	(683)
Ending Allowance	128	746	128	746	610
Provision (recapture)	(176)	(332)	(488)	(683)
Consumer loans \| Single-family residential
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	33,679	40,963	38,880	40,523	40,523
Charge-offs	0	0	(82)	(338)	(338)
Recoveries	11	105	23	568
Provision & Transfers	(4,186)	(1,070)	(9,317)	(755)
Ending Allowance	29,504	39,998	29,504	39,998	38,880
Provision (recapture)	(4,186)	(1,070)	(9,317)	(755)
Consumer loans \| Land - consumer lot loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	1,821	2,415	2,105	2,564	2,564
Charge-offs	0	0	0	0
Recoveries	0	0	0	1
Provision & Transfers	(114)	(138)	(398)	(288)
Ending Allowance	1,707	2,277	1,707	2,277	2,105
Provision (recapture)	(114)	(138)	(398)	(288)
Consumer loans \| HELOC
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	2,850	3,257	3,069	3,049	3,049
Charge-offs	0	0	0	0
Recoveries	1	1	2	2
Provision & Transfers	(87)	(136)	(307)	71
Ending Allowance	2,764	3,122	2,764	3,122	3,069
Provision (recapture)	(87)	(136)	(307)	71
Consumer loans \| Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	2,806	3,717	2,922	2,817	2,817
Charge-offs	(857)	(215)	(1,561)	(957)	(1,334)
Recoveries	90	41	214	280
Provision & Transfers	823	(292)	1,287	1,111
Ending Allowance	2,862	3,251	2,862	3,251	$ 2,922
Provision (recapture)	823	(292)	1,287	1,111
Unfunded commitments
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provision & Transfers	(3,500)	500	(2,500)	(1,000)
Provision (recapture)	$ (3,500)	$ 500	$ (2,500)	$ (1,000)

Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477657/942-210-S45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478478/942-210-S50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(7)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
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-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
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-Publisher FASB
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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