Allowance for Loan Losses and Credit Quality Information - Schedule of Loans Identified as Troubled Debt Restructurings During Periods Indicated (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	$ 493	$ 1,282	$ 2,306	$ 1,629
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	141	557	1,125	557
Residential [Member]
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	112	197	726	409
Consumer Loan Commitments [Member]
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	$ 240	$ 528	$ 455	$ 663