Fair Value Measurements - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Financial Assets:
Cash and due from banks	$ 5,087	$ 4,851
Interest-bearing deposits	6,826	7,501
Certificates of deposit	3,472	4,216
Federal funds sold	336	2,350
Securities available-for-sale	49,826	51,173
Restricted securities	3,756	2,649
Loans, net	401,268	381,537
Loans held for sale		276
Accrued interest receivable	1,321	1,372
Bank owned life insurance	9,944	9,869
Mortgage servicing rights	692	671
Financial Liabilities:
Non-interest-bearing liabilities	77,369	74,799
Savings and other interest-bearing deposits	169,027	178,869
Time deposits	136,104	128,050
Securities sold under repurchase agreements	8,489	18,310
FHLB advances	60,000	35,000
Subordinated debt	6,864	6,860
Accrued interest payable	225	331
Financial Assets:
Cash and due from banks	5,087	4,851
Interest-bearing deposits	6,826	7,501
Certificates of deposit	3,472	4,216
Federal funds sold	336	2,350
Securities available-for-sale	49,826	51,173
Restricted securities	3,756	2,649
Loans, net	400,988	384,468
Loans held for sale		276
Accrued interest receivable	1,321	1,372
Bank owned life insurance	9,944	9,869
Mortgage servicing rights	692	671
Financial Liabilities:
Non-interest-bearing liabilities	77,369	74,799
Savings and other interest-bearing deposits	167,027	178,869
Time deposits	135,662	127,497
Securities sold under repurchase agreements	8,489	18,310
FHLB advances	59,352	35,668
Subordinated debt	7,000	7,000
Accrued interest payable	225	331
Fair Value, Inputs, Level 1
Financial Assets:
Cash and due from banks	5,087	4,851
Interest-bearing deposits	6,826	7,501
Federal funds sold	336	2,350
Bank owned life insurance	9,944	9,869
Financial Liabilities:
Non-interest-bearing liabilities	77,369	74,799
Fair Value, Inputs, Level 2
Financial Assets:
Securities available-for-sale	43,111	43,469
Financial Assets:
Certificates of deposit	3,472	4,216
Securities available-for-sale	43,111	43,469
Accrued interest receivable	1,321	1,372
Financial Liabilities:
Savings and other interest-bearing deposits	167,027	178,869
Securities sold under repurchase agreements	8,489	18,310
FHLB advances	59,352	35,668
Accrued interest payable	225	331
Fair Value, Inputs, Level 3
Financial Assets:
Securities available-for-sale	6,715	7,704
Financial Assets:
Securities available-for-sale	6,715	7,704
Restricted securities	3,756	2,649
Loans, net	400,988	384,468
Loans held for sale		276
Mortgage servicing rights	692	671
Financial Liabilities:
Time deposits	135,662	127,497
Subordinated debt	$ 7,000	$ 7,000