Fair Value Measurements - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financial Assets:
Cash and due from banks	$ 4,851	$ 4,969
Interest-bearing deposits	7,501	15,330
Certificates of deposit	4,216	5,735
Federal funds sold	2,350	271
Securities available-for-sale	51,173	54,090
Restricted securities	2,649	2,731
Loans, net	381,537	343,323
Loans held for sale	276	270
Accrued interest receivable	1,372	1,318
Mortgage servicing rights	671	658
Financial Liabilities:
Non-interest-bearing liabilities	74,799	65,842
Savings and other interest-bearing deposits	178,869	166,628
Time deposits	128,050	127,388
Securities sold under repurchase agreements	18,310	7,161
FHLB advances	35,000	40,000
Subordinated debt	6,860	6,844
Accrued interest payable	331	318
Financial Assets:
Cash and due from banks	4,851	4,969
Interest-bearing deposits	7,501	15,330
Certificates of deposit	4,216	5,735
Federal funds sold	2,350	271
Securities available-for-sale	51,173	54,090
Restricted securities	2,649	2,731
Loans, net	384,468	347,500
Loans held for sale	276	270
Accrued interest receivable	1,372	1,318
Mortgage servicing rights	671	658
Financial Liabilities:
Non-interest-bearing liabilities	74,799	65,842
Savings and other interest-bearing deposits	178,869	166,628
Time deposits	127,497	127,433
Securities sold under repurchase agreements	18,310	7,161
FHLB advances	35,668	40,855
Subordinated debt	7,000	7,000
Accrued interest payable	331	318
Fair Value, Inputs, Level 1
Financial Assets:
Securities available-for-sale		1,216
Financial Assets:
Cash and due from banks	4,851	4,969
Interest-bearing deposits	7,501	15,330
Federal funds sold	2,350	271
Securities available-for-sale		1,216
Financial Liabilities:
Non-interest-bearing liabilities	74,799	65,842
Fair Value, Inputs, Level 2
Financial Assets:
Securities available-for-sale	43,469	48,929
Financial Assets:
Certificates of deposit	4,216	5,487
Securities available-for-sale	43,469	48,929
Accrued interest receivable	1,372	1,318
Financial Liabilities:
Savings and other interest-bearing deposits	178,869	166,628
Securities sold under repurchase agreements	18,310	7,161
FHLB advances	35,668	40,855
Accrued interest payable	331	318
Fair Value, Inputs, Level 3
Financial Assets:
Securities available-for-sale	7,704	3,945
Financial Assets:
Certificates of deposit		248
Securities available-for-sale	7,704	3,945
Restricted securities	2,649	2,731
Loans, net	384,468	347,500
Loans held for sale	276	270
Mortgage servicing rights	671	658
Financial Liabilities:
Time deposits	127,497	127,433
Subordinated debt	$ 7,000	$ 7,000