Securities - Additional Information (Detail) $ in Thousands	Dec. 31, 2018 USD ($) Security	Dec. 31, 2017 USD ($) Security
Schedule of Available-for-sale Securities [Line Items]
Fair value of securities	$ 17,500	$ 19,400
Debt Securities, Available-for-sale, Restriction Type [Extensible List]	us-gaap:CollateralPledgedMember	us-gaap:CollateralPledgedMember
Securities sold under repurchase agreements	$ 6,089	$ 9,498
Company's investment in Federal Home Loan Bank stock	5,100	3,700
Company's investment in Federal Reserve Bank stock	2,300	1,900
Investment in primary correspondent bank stock	$ 220	$ 220
US Government Agencies and Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Securities with unrealized loss positions | Security	54	36
State and Municipal Obligations
Schedule of Available-for-sale Securities [Line Items]
Securities with unrealized loss positions | Security	39	34
Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Securities with unrealized loss positions | Security	5	1