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Loans Receivable - Narrative (Details)	3 Months Ended
	Dec. 31, 2024 USD ($) portfolioSegment	Sep. 30, 2024 USD ($)
Receivables [Abstract]
Number of portfolio segments for loans held for investment | portfolioSegment	2
Accrued interest receivables for loans	$ 91,214,000	$ 92,362,000
Loans pledged to secure borrowings from the Federal Home Loan Bank	13,985,988,000
Nonaccrual interest income recognized	761,000
Individually evaluated for credit loss, interest income	924,000
Loan modified, subsequent default	$ 0

X

- Definition

Amount of the collateral pledged in support of federal home loan bank advances outstanding.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 470
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478878/942-470-45-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477734/942-470-50-3

+ Details

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Balance Type:	debit
Period Type:	instant

X

- Definition

Amount, before allowance for credit loss, of accrued interest on financing receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amortized cost excluding accrued interest, of financing receivable with payment default in current period and modified within previous 12 months preceding payment default for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 44
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-44

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Period Type:	duration

X

- Definition

Amount of interest income on financing receivable on nonaccrual status.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-16

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Period Type:	duration

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- References

No definition available.

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X

- Definition

Financing Receivable, Individually Evaluated for Credit Loss, Interest Income

+ References

No definition available.

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X

- Definition

Number Of Portfolio Segments For Loans Held For Investment

+ References

No definition available.

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