Allowance for Loan Losses - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) Property	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) Property Person	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) Property
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period of nonperforming loans			90 days
Non-accruing loans excluded from impaired loan	$ 760,000		$ 760,000		$ 465,000
Non-accruing loans accrued interest	6,000	$ 3,000	9,000	$ 3,000
Loans modified as TDRs	$ 0	$ 0	$ 0	$ 0
No. of Properties | Property	30		30		14
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential properties collateralized with loan | Property			2
Residential mortgage loan amount	$ 127,000		$ 127,000
No. of Borrowers | Person			2
No. of Properties | Property	5		5		2
Residential | Other assets
Accounts, Notes, Loans and Financing Receivable [Line Items]
Properties marketed for sale, value	$ 708,000		$ 708,000
No. of Properties | Property	1		1
Branch Office | Other assets
Accounts, Notes, Loans and Financing Receivable [Line Items]
Properties marketed for sale, value					$ 403,000
No. of Properties | Property					1
Residential First Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Minimum balance in order to assign a risk rating grade	$ 1,000,000		$ 1,000,000
Consumer and Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Minimum balance in order to assign a risk rating grade	$ 250,000		$ 250,000