Allowance for Loan Losses and Credit Quality Information - Analysis of Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	$ 51,707	$ 43,282	$ 56,498
Loans with No Specific Reserve	33,641	26,005
Loans with Specific Reserve	18,066	17,277
Related Specific Reserve	5,068	4,903
Contractual Principal Balances	62,450	65,644
Average Loan Balances	50,574	51,803
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	4,583	5,003	4,991
Loans with No Specific Reserve	2,347	2,362
Loans with Specific Reserve	2,236	2,641
Related Specific Reserve	1,865	1,781
Contractual Principal Balances	6,146	13,013
Average Loan Balances	5,292	5,347
Owner-Occupied Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	6,318	5,197	13,263
Loans with No Specific Reserve	4,564	5,184
Loans with Specific Reserve	1,754	12
Related Specific Reserve	1,191	12
Contractual Principal Balances	6,906	8,293
Average Loan Balances	10,005	11,542
Commercial Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	15,786	8,661	11,240
Loans with No Specific Reserve	10,513	2,784
Loans with Specific Reserve	5,273	5,877
Related Specific Reserve	1,019	1,987
Contractual Principal Balances	20,587	16,566
Average Loan Balances	11,074	10,444
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	1,070	1,158	1,216
Loans with No Specific Reserve	1,070	1,158
Loans with Specific Reserve
Related Specific Reserve
Contractual Principal Balances	1,563	1,563
Average Loan Balances	873	968
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	18,413	17,852	19,578
Loans with No Specific Reserve	10,994	9,750
Loans with Specific Reserve	7,419	8,103
Related Specific Reserve	807	989
Contractual Principal Balances	21,030	20,153
Average Loan Balances	18,033	18,047
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ending Loan Balances	5,537	5,411	6,210
Loans with No Specific Reserve	4,153	4,767
Loans with Specific Reserve	1,384	644
Related Specific Reserve	186	134
Contractual Principal Balances	6,218	6,056
Average Loan Balances	$ 5,297	$ 5,455