Loans - Allowance for Loan Loss Account by Loan (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	$ 4,826	$ 6,112	$ 6,112
Charge off	(275)	(239)	(3,159)
Recovery	35		1,396
Provision for Loan Loss	68	291	477
Ending balance	4,654		4,826
Multi-Family [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	314	412	412
Recovery			417
Provision for Loan Loss	1		(515)
Ending balance	315		314
One-to-Four Family Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	747	852	852
Charge off	(6)		(66)
Recovery	3		13
Provision for Loan Loss	68		(52)
Ending balance	812		747
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	189	260	260
Recovery	2		12
Provision for Loan Loss	(2)		(83)
Ending balance	189		189
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	161	277	277
Provision for Loan Loss	95		(116)
Ending balance	256		161
Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	1,223	1,760	1,760
Charge off			(2,608)
Recovery			559
Provision for Loan Loss	(520)		1,512
Ending balance	703		1,223
Non-Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	789	964	964
Recovery	4		16
Provision for Loan Loss	66		(191)
Ending balance	859		789
Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	367	778	778
Recovery	1		10
Provision for Loan Loss	29		(421)
Ending balance	397		367
Junior Liens [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	5	8	8
Recovery			4
Provision for Loan Loss	1		(7)
Ending balance	6		5
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	184	208	208
Charge off	(69)		(261)
Recovery	23		87
Provision for Loan Loss	94		150
Ending balance	232		184
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	847	$ 593	593
Charge off	(200)		(224)
Recovery	2		278
Provision for Loan Loss	236		200
Ending balance	$ 885		$ 847