Regulatory Capital Requirements - Bank's Actual Capital Ratios (Detail) $ in Thousands	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Banking And Thrift Other Disclosures [Abstract]
Actual, Amount	$ 199,019	$ 192,423
For capital adequacy purposes, Amount	110,039	112,039
To be well capitalized, Amount	137,549	140,049
Actual, Amount	181,814	176,971
For capital adequacy purposes, Amount	82,529	84,029
To be well capitalized, Amount	110,039	112,039
Actual, Amount	181,814	176,971
For capital adequacy purposes, Amount	61,897	63,022
To be well capitalized, Amount	89,407	91,032
Actual, Amount	181,814	176,971
For capital adequacy purposes, Amount	72,390	77,919
To be well capitalized, Amount	$ 90,488	$ 97,399
Actual, Ratio	0.145	0.137
For capital adequacy purposes, Ratio	0.080	0.080
To be well capitalized, Ratio	0.100	0.100
Actual, Ratio	0.132	0.126
For capital adequacy purposes, Ratio	0.060	0.060
To be well capitalized, Ratio	0.080	0.080
Actual, Ratio	13.20%	12.60%
For capital adequacy purposes, Ratio	4.50%	4.50%
To be well capitalized, Ratio	6.50%	6.50%
Actual, Ratio	10.00%	9.10%
For capital adequacy purposes, Ratio	4.00%	4.00%
To be well capitalized, Ratio	5.00%	5.00%