Loans and Allowance for Loan Losses - Troubled Debt Restructurings (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Number of Loans	1	2	1	2
Pre-Modification Principal Balance	$ 126	$ 4,930	$ 126	$ 4,930
Post-Modification Principal Balance	$ 126	$ 4,932	$ 126	$ 4,932
Residential real estate [Member]
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Number of Loans		1		1
Pre-Modification Principal Balance		$ 1,099		$ 1,099
Post-Modification Principal Balance		$ 1,100		$ 1,100
SBA commercial real estate
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Number of Loans		1		1
Pre-Modification Principal Balance		$ 3,831		$ 3,831
Post-Modification Principal Balance		$ 3,832		$ 3,832
Commercial business
Troubled Debt Restructuring, Debtor, Subsequent Periods [Line Items]
Number of Loans	1		1
Pre-Modification Principal Balance	$ 126		$ 126
Post-Modification Principal Balance	$ 126		$ 126

Number of financing receivables that have been modified by troubled debt restructurings.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

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Amount, after troubled debt restructuring, of modified financing receivable.

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Amount, before troubled debt restructuring, of financing receivable to be modified.

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