Allowance for Loan Losses and Credit Quality Information - Analysis of Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	$ 45,840	$ 43,282	$ 52,052
Loans with No Specific Reserve	26,906	26,005
Loans with Specific Reserve	18,934	17,277
Related Specific Reserve	4,401	4,903
Contractual Principal Balances	55,685	65,644
Average Loan Balances	48,442	51,803
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	4,109	5,003	6,048
Loans with No Specific Reserve	1,592	2,362
Loans with Specific Reserve	2,517	2,641
Related Specific Reserve	1,881	1,781
Contractual Principal Balances	5,131	13,013
Average Loan Balances	5,115	5,347
Owner-Occupied Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	4,928	5,197	12,681
Loans with No Specific Reserve	2,615	5,184
Loans with Specific Reserve	2,313	12
Related Specific Reserve	1,157	12
Contractual Principal Balances	5,718	8,293
Average Loan Balances	8,338	11,542
Commercial Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	13,483	8,661	10,791
Loans with No Specific Reserve	8,210	2,784
Loans with Specific Reserve	5,273	5,877
Related Specific Reserve	307	1,987
Contractual Principal Balances	18,268	16,566
Average Loan Balances	11,523	10,444
Construction Loan Commitments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances		1,158
Loans with No Specific Reserve		1,158
Loans with Specific Reserve
Related Specific Reserve
Contractual Principal Balances		1,563
Average Loan Balances	630	968
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	17,743	17,852	16,961
Loans with No Specific Reserve	10,090	9,750
Loans with Specific Reserve	7,653	8,103
Related Specific Reserve	872	989
Contractual Principal Balances	20,220	20,153
Average Loan Balances	17,666	18,047
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	5,577	5,411	4,925
Loans with No Specific Reserve	4,399	4,767
Loans with Specific Reserve	1,178	644
Related Specific Reserve	184	134
Contractual Principal Balances	6,348	6,056
Average Loan Balances	$ 5,170	$ 5,455