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, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	$ 1,282	$ 1,838	$ 1,629	$ 2,480
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	557	121	557	121
Residential [Member]
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	197	1,565	409	1,844
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	$ 528	$ 152	$ 663	$ 515