Fair Value Measurements - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financial Assets:
Cash and due from banks	$ 5,280	$ 4,969	[1]
Interest-bearing deposits	6,343	15,330	[1]
Certificates of deposit	4,464	5,735	[1]
Federal funds sold	460	271	[1]
Securities available-for-sale	52,563	54,090	[1]
Restricted securities	2,209	2,731	[1]
Loans, net	364,822	343,323	[1]
Loans held for sale	481	270	[1]
Accrued interest receivable	1,241	1,318	[1]
Mortgage servicing rights	590	658
Financial Liabilities:
Non-interest-bearing liabilities	74,615	65,842	[1]
Savings and other interest-bearing deposits	175,448	166,628	[1]
Time deposits	127,912	127,388	[1]
Securities sold under repurchase agreements	12,984	7,161	[1]
FHLB advances	25,000	40,000	[1]
Subordinated debt	6,856	6,844	[1]
Accrued interest payable	207	318
Financial Assets:
Cash and due from banks	5,280	4,969
Interest-bearing deposits	6,343	15,330
Certificates of deposit	4,464	5,735
Federal funds sold	460	271
Securities available-for-sale	52,563	54,090	[1]
Restricted securities	2,209	2,731
Loans, net	371,247	347,500
Loans held for sale	481	270
Accrued interest receivable	1,241	1,318
Mortgage servicing rights	590	658	[1]
Financial Liabilities:
Non-interest-bearing liabilities	74,615	65,842
Savings and other interest-bearing deposits	175,448	166,628
Time deposits	129,175	127,433
Securities sold under repurchase agreements	12,984	7,161
FHLB advances	25,755	40,855
Subordinated debt	7,000	7,000
Accrued interest payable	207	318
Fair Value, Inputs, Level 1
Financial Assets:
Securities available-for-sale	1,597	1,216
Financial Assets:
Cash and due from banks	5,280	4,969
Interest-bearing deposits	6,343	15,330
Federal funds sold	460	271
Securities available-for-sale	1,597	1,216
Financial Liabilities:
Non-interest-bearing liabilities	74,615	65,842
Fair Value, Inputs, Level 2
Financial Assets:
Securities available-for-sale	45,463	48,929
Financial Assets:
Certificates of deposit	4,464	5,487
Securities available-for-sale	45,463	48,929
Accrued interest receivable	1,241	1,318
Financial Liabilities:
Savings and other interest-bearing deposits	175,448	166,628
Securities sold under repurchase agreements	12,984	7,161
FHLB advances	25,755	40,855
Accrued interest payable	207	318
Fair Value, Inputs, Level 3
Financial Assets:
Securities available-for-sale	5,503	3,945
Financial Assets:
Certificates of deposit		248
Securities available-for-sale	5,503	3,945
Restricted securities	2,209	2,731
Loans, net	371,247	347,500
Loans held for sale	481	270
Mortgage servicing rights	590	658
Financial Liabilities:
Time deposits	129,175	127,433
Subordinated debt	$ 7,000	$ 7,000

[1] Derived from Audited December 31, 2015 Financial Statements