Non-performing Loans and Impaired Loans - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2017 USD ($) ConsecutivePayment Contract	Dec. 31, 2016 USD ($)
Financing Receivable, Modifications [Line Items]
Non-accrual loans	$ 6,944,000	$ 7,936,000
Non-performing TDRs	998,000
Loans acquired included in non-accrual loans	2,200,000
Loans acquired included in non-performing TDRs	$ 17,000
Loan delinquency period	90 days
Minimum period required for satisfactory performance to return loan from non-accrual to accrual status	6 months
Restructured loans with modified recorded balances	$ 0
Restructured loan returned to accruing status number of Consecutive Payments of loan | ConsecutivePayment	6
Restructured loan reported in TDRs	$ 2,600,000
Specific reserves allocated to troubled debt restructuring	$ 0
Number TDRs returned to accrual status | Contract	0
Loans classified as TDR after a period	90 days
Performing Financing Receivable [Member]
Financing Receivable, Modifications [Line Items]
Restructured loan	$ 1,600,000
Good Pass [Member]
Financing Receivable, Modifications [Line Items]
Number of consecutive years of profit Unaudited Financial Information for Good Pass Rating	5 years
Number of years of Satisfactory Relationship with bank for Good Pass Rating	5 years
Minimum [Member]
Financing Receivable, Modifications [Line Items]
Loan delinquency period	90 days
Delay or shortfall in payments of loan	30 days
Loans with an aggregate credit exposure	$ 1,000,000
Minimum [Member] | Good Pass [Member]
Financing Receivable, Modifications [Line Items]
Number of consecutive years of profit for Good Pass Rating	3 years
Minimum [Member] | Satisfactory Pass [Member]
Financing Receivable, Modifications [Line Items]
Minimum number of years of Satisfactory Repayment required for Satisfactory Pass Rating	2 years
Maximum [Member]
Financing Receivable, Modifications [Line Items]
Loans with an aggregate credit exposure	$ 2,500,000