Loans Receivable and Related Allowance for Loan Losses (10) (Detail) $ in Thousands	6 Months Ended	12 Months Ended
	Mar. 31, 2022 USD ($) Number	Sep. 30, 2021 USD ($) Number
Financing Receivable, Impaired [Line Items]
Number of Loans | Number	4	8
Loan Modified Exposure	$ 42,321	$ 61,234
Gross Loans	$ 808,037	$ 913,824
Percentage of Gross Loans on Modified	5.24%	6.70%
Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Gross Loans	$ 101,354	$ 115,246
Percentage of Gross Loans on Modified	0.00%	0.00%
Residential Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Number of Loans | Number		2
Loan Modified Exposure		$ 667
Gross Loans	$ 177,669	$ 198,710
Percentage of Gross Loans on Modified	0.00%	0.07%
Construction and Development - Residential and Commercial [Member]
Financing Receivable, Impaired [Line Items]
Gross Loans	$ 25,558	$ 61,492
Percentage of Gross Loans on Modified	0.00%	0.00%
Construction And Development Land
Financing Receivable, Impaired [Line Items]
Gross Loans	$ 4,603	$ 2,204
Percentage of Gross Loans on Modified	0.00%	0.00%
Construction And Development [Member]
Financing Receivable, Impaired [Line Items]
Gross Loans	$ 30,161	$ 63,696
Percentage of Gross Loans on Modified	0.00%	0.00%
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Number of Loans | Number	4	6
Loan Modified Exposure	$ 42,321	$ 60,567
Gross Loans	$ 400,974	$ 426,915
Percentage of Gross Loans on Modified	5.24%	6.63%
Commercial Farmland [Member]
Financing Receivable, Impaired [Line Items]
Gross Loans	$ 15,624	$ 10,297
Percentage of Gross Loans on Modified	0.00%	0.00%
Commercial Multi Family [Member]
Financing Receivable, Impaired [Line Items]
Gross Loans	$ 54,789	$ 66,332
Percentage of Gross Loans on Modified	0.00%	0.00%
Commercial - Other [Member]
Financing Receivable, Impaired [Line Items]
Gross Loans	$ 7,977	$ 10,954
Percentage of Gross Loans on Modified	0.00%	0.00%
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Number of Loans | Number	4	6
Loan Modified Exposure	$ 42,321	$ 60,567
Gross Loans	$ 580,718	$ 629,744
Percentage of Gross Loans on Modified	5.24%	6.63%
Consumer - Home Equity Lines of Credit [Member]
Financing Receivable, Impaired [Line Items]
Gross Loans	$ 12,283	$ 13,491
Percentage of Gross Loans on Modified	0.00%	0.00%
Consumer - Second Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Gross Loans	$ 4,969	$ 5,884
Percentage of Gross Loans on Modified	0.00%	0.00%
Consumer - Other [Member]
Financing Receivable, Impaired [Line Items]
Gross Loans	$ 2,237	$ 2,299
Percentage of Gross Loans on Modified	0.00%	0.00%
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Gross Loans	$ 19,489	$ 21,674
Percentage of Gross Loans on Modified	0.00%	0.00%