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
	Mar. 31, 2016	Mar. 31, 2015
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	$ 1,813	$ 347
Commercial Loan Commitments [Member]
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	984
Residential [Member]
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	614	212
Consumer Loan Commitments [Member]
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	$ 215	$ 135