Fair Value Measurements - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Financial Assets:
Cash and due from banks	$ 7,454	$ 4,851	[1]
Interest-bearing deposits	26,998	7,945	[1]
Certificates of deposit	3,224	4,216	[1]
Federal funds sold	6,559	1,906	[1]
Securities available-for-sale	54,448	51,173	[1]
Restricted securities	4,662	2,649	[1]
Loans, net	645,701	381,537	[1]
Loans held for sale	55,620	276	[1]
Accrued interest receivable	2,624	1,372	[1]
Bank owned life insurance	18,508	9,869	[1]
Mortgage servicing rights	989	671
Financial Liabilities:
Non-interest-bearing liabilities	97,299	74,799	[1]
Savings and other interest-bearing deposits	282,056	178,869	[1]
Time deposits	309,619	128,050	[1]
Securities sold under repurchase agreements	10,786	18,310	[1]
FHLB advances	70,000	35,000	[1]
Subordinated debt	6,868	6,860	[1]
Accrued interest payable	395	331
Financial Assets:
Cash and due from banks	7,454	4,851
Interest-bearing deposits	26,998	7,945
Certificates of deposit	3,224	4,216
Federal funds sold	6,559	1,906
Securities available-for-sale	54,448	51,173	[1]
Restricted securities	4,662	2,649
Loans, net	654,263	384,468
Loans held for sale	55,620	276
Accrued interest receivable	2,624	1,372
Bank owned life insurance	18,508	9,869
Mortgage servicing rights	989	671	[1]
Financial Liabilities:
Non-interest-bearing liabilities	97,299	74,799
Savings and other interest-bearing deposits	282,056	178,869
Time deposits	308,952	127,497
Securities sold under repurchase agreements	10,786	18,310
FHLB advances	70,591	35,668
Subordinated debt	7,000	7,000
Accrued interest payable	395	331
Fair Value, Inputs, Level 1
Financial Assets:
Cash and due from banks	7,454	4,851
Interest-bearing deposits	26,998	7,945
Federal funds sold	6,559	1,906
Bank owned life insurance	18,508	9,869
Financial Liabilities:
Non-interest-bearing liabilities	97,299	74,799
Fair Value, Inputs, Level 2
Financial Assets:
Securities available-for-sale	47,733	43,469
Financial Assets:
Certificates of deposit	3,224	4,216
Securities available-for-sale	47,733	43,469
Accrued interest receivable	2,624	1,372
Financial Liabilities:
Savings and other interest-bearing deposits	282,056	178,869
Securities sold under repurchase agreements	10,786	18,310
FHLB advances	70,591	35,668
Accrued interest payable	395	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	4,662	2,649
Loans, net	654,263	384,468
Loans held for sale	55,620	276
Mortgage servicing rights	989	671
Financial Liabilities:
Time deposits	308,952	127,497
Subordinated debt	$ 7,000	$ 7,000

[1] Derived from the audited December 31, 2016 Consolidated Financial Statements