Allowance for Loan Losses - Age Analysis of Past Due Loans Segregated by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Current	$ 3,531,605	$ 3,266,474
Financing Receivable, Recorded Investment, 30 to 59 Days Past Due	8,535	21,632
Financing Receivable, Recorded Investment, 60 to 89 Days Past Due	3,605	3,558
Financing Receivable, Recorded Investment, Non-performing	22,454	54,958
Financing Receivable, Recorded Investment, Past Due Loans, Total	34,594	80,148
Total Portfolio Loans	3,566,199	3,346,622
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Current	1,595,590	1,418,934
Financing Receivable, Recorded Investment, 30 to 59 Days Past Due	1,209	2,230
Financing Receivable, Recorded Investment, 60 to 89 Days Past Due	207	413
Financing Receivable, Recorded Investment, Non-performing	10,750	30,556
Financing Receivable, Recorded Investment, Past Due Loans, Total	12,166	33,199
Total Portfolio Loans	1,607,756	1,452,133
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Current	836,276	780,315
Financing Receivable, Recorded Investment, 30 to 59 Days Past Due	2,599	4,409
Financing Receivable, Recorded Investment, 60 to 89 Days Past Due	278	237
Financing Receivable, Recorded Investment, Non-performing	3,296	6,435
Financing Receivable, Recorded Investment, Past Due Loans, Total	6,173	11,081
Total Portfolio Loans	842,449	791,396
Commercial Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Current	139,133	150,823
Financing Receivable, Recorded Investment, 30 to 59 Days Past Due	1,049	10,542
Financing Receivable, Recorded Investment, 60 to 89 Days Past Due	751
Financing Receivable, Recorded Investment, Non-performing	2,742	6,778
Financing Receivable, Recorded Investment, Past Due Loans, Total	4,542	17,320
Total Portfolio Loans	143,675	168,143
Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Current	481,260	416,364
Financing Receivable, Recorded Investment, 30 to 59 Days Past Due	828	1,713
Financing Receivable, Recorded Investment, 60 to 89 Days Past Due	1,666	1,948
Financing Receivable, Recorded Investment, Non-performing	3,338	7,278
Financing Receivable, Recorded Investment, Past Due Loans, Total	5,832	10,939
Total Portfolio Loans	487,092	427,303
Home Equity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Current	408,777	424,485
Financing Receivable, Recorded Investment, 30 to 59 Days Past Due	2,468	2,332
Financing Receivable, Recorded Investment, 60 to 89 Days Past Due	659	865
Financing Receivable, Recorded Investment, Non-performing	2,291	3,653
Financing Receivable, Recorded Investment, Past Due Loans, Total	5,418	6,850
Total Portfolio Loans	414,195	431,335
Installment and Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Current	67,420	73,334
Financing Receivable, Recorded Investment, 30 to 59 Days Past Due	382	406
Financing Receivable, Recorded Investment, 60 to 89 Days Past Due	44	95
Financing Receivable, Recorded Investment, Non-performing	37	40
Financing Receivable, Recorded Investment, Past Due Loans, Total	463	541
Total Portfolio Loans	67,883	73,875
Consumer Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Current	3,149	2,219
Financing Receivable, Recorded Investment, Non-performing		218
Financing Receivable, Recorded Investment, Past Due Loans, Total		218
Total Portfolio Loans	$ 3,149	$ 2,437