Allowance for Loan Losses - Additional Information (Detail) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2016 USD ($) SecurityLoan	Sep. 30, 2015	Mar. 31, 2015 SecurityLoan	Dec. 31, 2014	Dec. 31, 2015 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period for calculating Loss migration rates of portfolio segments	3 years
Allowance for loan losses	$ 14,433				$ 14,361
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
Impaired loans	Greater than $350
Allowance for loan losses recorded for acquired loans	$ 113
Foreclosed assets	57				116
TDRs [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	246				$ 286
Scenario, Previously Reported [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period for calculating Loss migration rates of portfolio segments		2 years
Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Foreclosed assets	57
Residential mortgages in process of foreclosure	$ 608
Purchased Automobile Loans Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period for calculating Loss migration rates of portfolio segments	2 years 7 months 6 days