Allowance for Loan Losses - Summary of Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	$ 48,106	$ 46,616	$ 47,911	$ 46,255
Charge-offs	(1,755)	(3,746)	(3,205)	(4,721)
Recoveries	404	4,844	842	5,891
Net (Charge-offs)/ Recoveries	(1,351)	1,098	(2,363)	1,170
Provision for loan losses	2,059	(1,134)	3,266	(845)
Balance at End of Period	48,814	46,580	48,814	46,580
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	19,071	19,880	20,164	18,921
Charge-offs	(310)	(1,737)	(376)	(2,004)
Recoveries	73	1,294	176	1,834
Net (Charge-offs)/ Recoveries	(237)	(443)	(200)	(170)
Provision for loan losses	184	1,296	(946)	1,982
Balance at End of Period	19,018	20,733	19,018	20,733
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	13,711	13,979	13,668	14,433
Charge-offs	(992)	(743)	(1,698)	(1,033)
Recoveries	89	2,936	203	3,249
Net (Charge-offs)/ Recoveries	(903)	2,193	(1,495)	2,216
Provision for loan losses	500	(3,168)	1,135	(3,645)
Balance at End of Period	13,308	13,004	13,308	13,004
Construction Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	6,869	5,183	6,093	5,374
Charge-offs		(664)		(692)
Recoveries	1	324	2	375
Net (Charge-offs)/ Recoveries	1	(340)	2	(317)
Provision for loan losses	801	(84)	1,576	(298)
Balance at End of Period	7,671	4,759	7,671	4,759
Consumer Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	6,723	6,408	6,333	6,362
Charge-offs	(177)	(425)	(552)	(547)
Recoveries	112	164	248	223
Net (Charge-offs)/ Recoveries	(65)	(261)	(304)	(324)
Provision for loan losses	369	558	998	667
Balance at End of Period	7,027	6,705	7,027	6,705
Other Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	1,732	1,166	1,653	1,165
Charge-offs	(276)	(177)	(579)	(445)
Recoveries	129	126	213	210
Net (Charge-offs)/ Recoveries	(147)	(51)	(366)	(235)
Provision for loan losses	205	264	503	449
Balance at End of Period	$ 1,790	$ 1,379	$ 1,790	$ 1,379