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, 2017	Mar. 31, 2016
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	$ 6,052	$ 1,813
Commercial
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	443	984
Commercial mortgages
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	0	0
Construction
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	1,712	0
Residential
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	242	614
Consumer
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	584	215
Owner-occupied commercial
Financing Receivable, Modifications [Line Items]
Total loans identified during the period	$ 3,071	$ 0