Investment Securities - Amortized Cost and Fair Value by Contractual Maturity - Securities Available for Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Available for Sale - Amortized Cost
Amortized Cost	$ 193,750	$ 187,778
Available for Sale - Fair Value
Fair Value	205,374	201,965
Municipal bonds
Available for Sale - Amortized Cost
Due within one year	8,501
Due after one year through five years	27,848
Due after five years through ten years	30,486
Due after ten years	104,651
Amortized Cost	170,986	168,472
Available for Sale - Fair Value
Due within one year	8,588
Due after one year through five years	29,071
Due after five years through ten years	32,508
Due after ten years	112,362
Fair Value	182,029	181,596
CMO
Available for Sale - Amortized Cost
Without single maturity date	9,741
Available for Sale - Fair Value
Without single maturity date	10,003
ABS
Available for Sale - Amortized Cost
Without single maturity date	794
Available for Sale - Fair Value
Without single maturity date	860
SBA certificates
Available for Sale - Amortized Cost
Without single maturity date	2,355
Amortized Cost	2,355	639
Available for Sale - Fair Value
Without single maturity date	2,333
Fair Value	2,333	$ 694
Mortgage-backed securities
Available for Sale - Amortized Cost
Without single maturity date	9,374
Available for Sale - Fair Value
Without single maturity date	$ 9,649

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 3
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121553693&loc=d3e26610-111562

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-Name Accounting Standards Codification
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-Section 50
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