Allowance for Loan Losses and Credit Quality Information - Schedule of Loans Identified as Troubled Debt Restructurings During Periods Indicated (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Financing Receivable, Modifications [Line Items]
Loans identified during the period	$ 1,838	$ 1,067	$ 2,480	$ 2,401
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Loans identified during the period	121	24	121	24
Commercial Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Loans identified during the period		826		1,061
Residential [Member]
Financing Receivable, Modifications [Line Items]
Loans identified during the period	1,565	173	1,844	599
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Loans identified during the period	$ 152	$ 44	$ 515	$ 717