Allowance for Loan Losses - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($) SecurityLoan	Jun. 30, 2016 USD ($) SecurityLoan	Jun. 30, 2017 USD ($) SecurityLoan	Jun. 30, 2016 USD ($) SecurityLoan	Dec. 31, 2016 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period for calculating Loss migration rates of portfolio segments			3 years
Allowance for loan losses	$ 13,047	$ 13,047	$ 13,047	$ 13,047	$ 13,305
Proceeds from payoff on previously charged-off loans		$ 1,303		$ 1,303
Number of days past due for loans to be considered as nonperforming			90 days
Reasonable period for nonperforming TDRs to be returned to performing status			6 months
Number of days reaching where loans are considered for nonaccrual status			90 days
Conditions where loans are considered for nonaccrual status			A loan may be returned to accruing status only if one of three conditions are met the loan is well-secured and none of the principal and interest has been past due for a minimum of 90 days; the loan is a TDR and has made a minimum of six months payments; or the principal and interest payments are reasonably assured and a sustained period of performance has occurred, generally six months.
Defaulted loans | SecurityLoan	0	0	0	0
Impaired loans				Greater than $350
Allowance for loan losses recorded for acquired loans			$ 155		175
Foreclosed assets	$ 27		27		37
TDRs [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	421		421		278
Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Foreclosed assets	27		27
Residential mortgages in process of foreclosure	$ 328		$ 328		$ 710