Loans Receivable, Net - Loan Balances by Loan Classification Allocated Between Past Due Performing and Non-performing (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Currently Performing	$ 661,498,000	$ 640,605,000
30 - 89 Days Past Due	809,000	393,000
More than 90 days past Due and still Accruing	0	88,000	$ 0
Non-accrual loans	1,430,000	1,285,000
Total loans, gross	663,737,000	642,371,000
Multi-Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Currently Performing	26,067,000	37,445,000
Total loans, gross	26,067,000	37,445,000
One-to-Four Family Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Currently Performing	174,962,000	163,030,000
30 - 89 Days Past Due	614,000	181,000
More than 90 days past Due and still Accruing		88,000
Non-accrual loans	62,000	266,000
Total loans, gross	175,638,000	163,565,000
Home Equity Line of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Currently Performing	32,525,000	35,295,000
30 - 89 Days Past Due	158,000
Non-accrual loans	98,000	402,000
Total loans, gross	32,781,000	35,697,000
Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Currently Performing	38,548,000	30,246,000
Non-accrual loans	152,000
Total loans, gross	38,700,000	30,246,000
Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Currently Performing	12,175,000	14,833,000
Non-accrual loans		40,000
Total loans, gross	12,175,000	14,873,000
Non-Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Currently Performing	241,809,000	224,743,000
30 - 89 Days Past Due		209,000
Non-accrual loans	581,000
Total loans, gross	242,390,000	224,952,000
Farmland [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Currently Performing	34,041,000	36,740,000
Non-accrual loans		111,000
Total loans, gross	34,041,000	36,851,000
Junior Liens [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Currently Performing	1,033,000	1,180,000
Non-accrual loans	4,000	4,000
Total loans, gross	1,037,000	1,184,000
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Currently Performing	8,408,000	8,614,000
30 - 89 Days Past Due	26,000	3,000
Non-accrual loans	8,000	3,000
Total loans, gross	8,442,000	8,620,000
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Currently Performing	91,930,000	88,479,000
30 - 89 Days Past Due	11,000
Non-accrual loans	525,000	459,000
Total loans, gross	$ 92,466,000	$ 88,938,000