Allowance for Loan Losses - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	$ 177,207	$ 172,808
Charge-offs	(293)	(228)
Recoveries	406	717
Provision & Transfers	2,000	3,500
Ending Allowance	179,320	176,797
Provision recapture	(2,000)	(3,500)
Unfunded commitments
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provision & Transfers	(2,000)	(1,000)
Provision recapture	2,000	1,000
Commercial loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	137,194	133,476
Charge-offs	(80)	(82)
Recoveries	84	52
Provision & Transfers	1,957	4,836
Ending Allowance	139,155	138,282
Provision recapture	(1,957)	(4,836)
Commercial loans \| Multi-family
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	13,155	12,013
Charge-offs	0	0
Recoveries	0	0
Provision & Transfers	636	311
Ending Allowance	13,791	12,324
Provision recapture	(636)	(311)
Commercial loans \| Commercial real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	28,842	25,814
Charge-offs	0	0
Recoveries	2	4
Provision & Transfers	163	1,562
Ending Allowance	29,007	27,380
Provision recapture	(163)	(1,562)
Commercial loans \| Commercial & industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	58,773	57,210
Charge-offs	(62)	(82)
Recoveries	32	32
Provision & Transfers	2,093	6,713
Ending Allowance	60,836	63,873
Provision recapture	(2,093)	(6,713)
Commercial loans \| Construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	29,408	26,161
Charge-offs	0	0
Recoveries	0	0
Provision & Transfers	(545)	(28)
Ending Allowance	28,863	26,133
Provision recapture	545	28
Commercial loans \| Land - acquisition & development
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	7,016	12,278
Charge-offs	(18)	0
Recoveries	50	16
Provision & Transfers	(390)	(3,722)
Ending Allowance	6,658	8,572
Provision recapture	390	3,722
Consumer loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	40,013	39,332
Charge-offs	(213)	(146)
Recoveries	322	665
Provision & Transfers	43	(1,336)
Ending Allowance	40,165	38,515
Provision recapture	(43)	1,336
Consumer loans \| Construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	2,781	3,410
Charge-offs	0	0
Recoveries	0	0
Provision & Transfers	(519)	90
Ending Allowance	2,262	3,500
Provision recapture	519	(90)
Consumer loans \| Single-family residential
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	28,029	25,518
Charge-offs	0	0
Recoveries	120	430
Provision & Transfers	407	(473)
Ending Allowance	28,556	25,475
Provision recapture	(407)	473
Consumer loans \| Land - consumer lot loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	3,512	5,047
Charge-offs	0	0
Recoveries	9	0
Provision & Transfers	(176)	(905)
Ending Allowance	3,345	4,142
Provision recapture	176	905
Consumer loans \| HELOC
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	2,859	2,482
Charge-offs	0	0
Recoveries	1	1
Provision & Transfers	113	105
Ending Allowance	2,973	2,588
Provision recapture	(113)	(105)
Consumer loans \| Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Allowance	2,832	2,875
Charge-offs	(213)	(146)
Recoveries	192	234
Provision & Transfers	218	(153)
Ending Allowance	3,029	2,810
Provision recapture	$ (218)	$ 153

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

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

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+ References

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- Definition

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

+ References

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

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-6

Reference 2: 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

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- Definition

Financing Receivable, Allowance for Credit Losses, Excluding Accrued Interest, Provision and Transfers

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