Allowance for Loan Losses - Summary of Allowance for Loan Losses and Recorded Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	$ 58		$ 97
Allowance for Loan Losses, Collectively Evaluated for Impairment	46,522		46,158
Total Allowance for Loan Losses	46,580	46,616	46,255	46,105	45,936	46,484
Portfolio Loans, Individually Evaluated for Impairment	46,209		52,856
Portfolio Loans, Collectively Evaluated for Impairment	3,678,870		3,513,343
Total Portfolio Loans	3,725,079		3,566,199
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0		0
Allowance for Loan Losses, Collectively Evaluated for Impairment	20,733		18,921
Total Allowance for Loan Losses	20,733	19,880	18,921	23,484	24,442	25,246
Portfolio Loans, Individually Evaluated for Impairment	21,228		26,968
Portfolio Loans, Collectively Evaluated for Impairment	1,615,155		1,580,788
Total Portfolio Loans	1,636,383		1,607,756
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0		0
Allowance for Loan Losses, Collectively Evaluated for Impairment	13,004		14,433
Total Allowance for Loan Losses	13,004	13,979	14,433	9,123	8,676	7,759
Portfolio Loans, Individually Evaluated for Impairment	9,545		9,580
Portfolio Loans, Collectively Evaluated for Impairment	912,646		832,869
Total Portfolio Loans	922,191		842,449
Commercial Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	0		25
Allowance for Loan Losses, Collectively Evaluated for Impairment	4,759		5,349
Total Allowance for Loan Losses	4,759	5,183	5,374	5,812	6,603	7,500
Portfolio Loans, Individually Evaluated for Impairment	8,179		8,072
Portfolio Loans, Collectively Evaluated for Impairment	180,132		135,603
Total Portfolio Loans	188,311		143,675
Consumer Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	47		53
Allowance for Loan Losses, Collectively Evaluated for Impairment	6,658		6,309
Total Allowance for Loan Losses	6,705	6,408	6,362	6,655	5,259	5,058
Portfolio Loans, Individually Evaluated for Impairment	7,129		8,079
Portfolio Loans, Collectively Evaluated for Impairment	905,227		896,357
Total Portfolio Loans	912,356		904,436
Other Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	11		19
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,368		1,146
Total Allowance for Loan Losses	1,379	1,166	1,165	1,031	956	921
Portfolio Loans, Individually Evaluated for Impairment	128		157
Portfolio Loans, Collectively Evaluated for Impairment	65,710		67,726
Total Portfolio Loans	$ 65,838		$ 67,883