Loans and Credit Quality (Narrative) (Detail)	9 Months Ended
	Sep. 30, 2016 USD ($) risk_rating		Sep. 30, 2015 USD ($)		Dec. 31, 2015 USD ($)
Loans [Line Items]
Loans and leases receivable, impaired, commitment to lend	$ 14,400,000				$ 9,700,000
Impaired Loans - Specific Reserve	11,862,000	[1]	$ 9,072,000	[1]	7,262,000
OREO Recorded Investment of Consumer Mortgage Loans Secured by Residential Real Estate Properties For Which Foreclosure Proceedings Are In Process	1,200,000				3,000,000
Covered Assets Recorded Investment of Properties For Which Foreclosure Proceedings Are In Process	172,000				775,000
Commercial Portfolio Segment [Member]
Loans [Line Items]
Impaired Loans - Specific Reserve	10,870,000	[1]	5,468,000	[1]	4,458,000
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	4,100,000
Commercial Real Estate Portfolio Segment [Member]
Loans [Line Items]
Impaired Loans - Specific Reserve	318,000	[1]	1,465,000	[1]	1,156,000
Financing Receivable, Modifications, Subsequent Default, Recorded Investment			$ 200,000
Nonperforming Financial Instruments [Member] | Contractual Interest Rate Reduction [Member]
Loans [Line Items]
Impaired Loans - Specific Reserve	3,400,000				3,900,000
Performing Financial Instruments [Member] | Contractual Interest Rate Reduction [Member]
Loans [Line Items]
Impaired Loans - Specific Reserve	$ 872,000				$ 4,000
Special Mention [Member]
Loans [Line Items]
Loans receivable risk rating | risk_rating	6
Potential Problem and Non-Performing [Member]
Loans [Line Items]
Loans receivable risk rating | risk_rating	7
Minimum [Member] | Pass [Member]
Loans [Line Items]
Loans receivable risk rating | risk_rating	1
Maximum [Member] | Nonperforming Financial Instruments [Member]
Loans [Line Items]
Loans receivable risk rating | risk_rating	8
Maximum [Member] | Loan Rated Five [Member]
Loans [Line Items]
Loans receivable risk rating | risk_rating	5

[1] Refer to Note 4 for additional information regarding impaired loans.