Loans - Summary of Non-accrual Loans by Loan Type (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Commercial loans	$ 2,004	$ 1,285
One-to-Four Family Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Commercial loans	521	266
Home Equity Line of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Commercial loans	530	402
Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Commercial loans	40	40
Farmland [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Commercial loans	111	111
Junior Liens [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Commercial loans	4	4
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Commercial loans	2	3
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Commercial loans	$ 796	$ 459