Allowance for Loan Losses - Additional Information (Detail)	3 Months Ended		12 Months Ended
	Mar. 31, 2017 USD ($) Property	Mar. 31, 2016 USD ($)	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	$ 671,000		$ 465,000
Non-accruing loans accrued interest	6,000		$ 2,000
Loans modified as TDRs	0	$ 0
Troubled debt restructuring subsequently defaulted	$ 0	$ 0
No. of Properties | Property	14		14
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential properties collateralized with loan | Property	0
No. of Properties | Property	2		2
Residential | Other assets
Accounts, Notes, Loans and Financing Receivable [Line Items]
Properties marketed for sale, value	$ 708,000
No. of Properties | Property	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
Consumer and Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Minimum balance in order to assign a risk rating grade	$ 250,000