Loans - Additional Information (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2017 USD ($) SecurityLoan	Dec. 31, 2016 USD ($) SecurityLoan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans past due more than 90 days and still accruing interest | $	$ 0	$ 0
Number of additional TDR	0	8
Number of lending relationships	2	3
Number of loans removed from TDR status	1
Troubled debt restructurings outstanding balance | $	$ 2,200,000
Number of additional TDR pay off	3
Loans that have been modified as TDRs, subsequently defaulted | $	$ 0
Commitments to lend additional funds to borrower | $	$ 0
Consumer Loans [Member] | Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fixed rate of interest period	1 year
Consumer Loans [Member] | Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fixed rate of interest period	5 years
Commercial Loans [Member] | Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fixed rate of interest period	1 year
Commercial Loans [Member] | Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fixed rate of interest period	5 years
Multi-Family [Member] | Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fixed rate of interest period	5 years
Multi-Family [Member] | Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans amortization period	20 years
One-to-Four Family Mortgages [Member] | Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable maturity period	30 years
Home Equity Line of Credit [Member] | Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable maturity period	10 years
Home Equity Line of Credit [Member] | Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable maturity period	15 years
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans amortization period	20 years
Construction [Member] | Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable maturity period	12 months
Construction [Member] | Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable maturity period	24 months
Recreational Land Development Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans amortization period	20 years
Recreational Land Development Loans [Member] | Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fixed rate of interest period	1 year
Recreational Land Development Loans [Member] | Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fixed rate of interest period	5 years
Farmland [Member] | Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fixed rate of interest period	5 years
Farmland [Member] | Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable maturity period	20 years
Fixed rate of interest period	10 years
Non-Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable maturity period	20 years
Number of lending relationships	1
Non-Residential Real Estate [Member] | Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fixed rate of interest period	5 years
Non-Residential Real Estate [Member] | Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fixed rate of interest period	10 years
Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases receivable in percentage	84.50%	84.00%