Fair Value Measurements and Disclosures about Fair Value of Financial Instruments (Carrying Value And Estimated Fair Value Of Financial Instruments) (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2015
Financial assets:
Cash and due from banks	$ 10,926		$ 11,449
Interest-bearing deposits with banks	30,164		17,893
Interest-bearing time deposits	2,555		3,100
Trading account securities	5,819		9,255
Securities available for sale	178,019		174,493
Securities held to maturity	2,955		3,166
Loans, net	564,771		518,611
FRB and FHLB stock	6,936		6,936
Accrued interest receivable	3,508		2,806
Loan servicing rights (included in other assets)	1,026	$ 783	310	$ 282	$ 156	$ 0
Financial liabilities:
Deposits	673,900		579,467
Repurchase agreements	1,347		1,345
Borrowings from FHLB	100,000		121,633
Accrued interest payable	265		195
Advance payments by borrowers for taxes and insurance	992		1,014
Small Business Administration Loans [Member]
Financial assets:
Loans, net	24,215		5,087
Residential mortgage loans held for sale [Member]
Financial assets:
Loans, net	755		384
Fair Value, Inputs, Level 1 [Member] | Small Business Administration Loans [Member]
Financial assets:
Loans, net	0		0
Fair Value, Inputs, Level 1 [Member] | Residential mortgage loans held for sale [Member]
Financial assets:
Loans, net	0		0
Fair Value, Inputs, Level 2 [Member] | Small Business Administration Loans [Member]
Financial assets:
Loans, net	24,215		5,087
Fair Value, Inputs, Level 2 [Member] | Residential mortgage loans held for sale [Member]
Financial assets:
Loans, net	755		384
Fair Value, Inputs, Level 3 [Member] | Small Business Administration Loans [Member]
Financial assets:
Loans, net	0		0
Fair Value, Inputs, Level 3 [Member] | Residential mortgage loans held for sale [Member]
Financial assets:
Loans, net	0		0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Financial assets:
Cash and due from banks	10,926		11,449
Interest-bearing deposits with banks	30,164		17,893
Interest-bearing time deposits	0		0
Trading account securities	0		0
Securities available for sale	0		0
Securities held to maturity	0		0
Loans, net	0		0
FRB and FHLB stock	0		0
Accrued interest receivable	0		0
Loan servicing rights (included in other assets)	0		0
Financial liabilities:
Deposits	0		0
Repurchase agreements	0		0
Borrowings from FHLB	0		0
Accrued interest payable	0		0
Advance payments by borrowers for taxes and insurance	0		0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Financial assets:
Cash and due from banks	0		0
Interest-bearing deposits with banks	0		0
Interest-bearing time deposits	2,556		3,114
Trading account securities	5,819		9,255
Securities available for sale	178,019		174,493
Securities held to maturity	3,343		3,654
Loans, net	0		0
FRB and FHLB stock	0		0
Accrued interest receivable	3,508		2,806
Loan servicing rights (included in other assets)	0		0
Financial liabilities:
Deposits	0		0
Repurchase agreements	1,347		1,345
Borrowings from FHLB	99,766		123,794
Accrued interest payable	265		195
Advance payments by borrowers for taxes and insurance	992		1,014
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Financial assets:
Cash and due from banks	0		0
Interest-bearing deposits with banks	0		0
Interest-bearing time deposits	0		0
Trading account securities	0		0
Securities available for sale	0		0
Securities held to maturity	0		0
Loans, net	557,854		522,560
FRB and FHLB stock	0		0
Accrued interest receivable	0		0
Loan servicing rights (included in other assets)	1,026		312
Financial liabilities:
Deposits	674,560		581,844
Repurchase agreements	0		0
Borrowings from FHLB	0		0
Accrued interest payable	0		0
Advance payments by borrowers for taxes and insurance	$ 0		$ 0