Allowance for Loan Losses - Summary of Allowance for Loan Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	$ 46,580	$ 46,105	$ 46,255	$ 46,484
Charge-offs	(1,002)	(2,991)	(5,488)	(10,054)
Recoveries	284	1,450	5,941	4,804
Net (Charge-offs)/ Recoveries	(718)	(1,541)	453	(5,250)
Provision for loan losses	1,454	3,419	608	6,749
Balance at End of Period	47,316	47,983	47,316	47,983
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	20,733	23,484	18,921	25,246
Charge-offs	0	(840)	(2,002)	(3,649)
Recoveries	(154)	617	1,681	2,939
Net (Charge-offs)/ Recoveries	(154)	(223)	(321)	(710)
Provision for loan losses	(602)	(5,572)	1,377	(6,847)
Balance at End of Period	19,977	17,689	19,977	17,689
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	13,004	9,123	14,433	7,759
Charge-offs	(37)	(759)	(1,070)	(2,682)
Recoveries	315	167	3,564	457
Net (Charge-offs)/ Recoveries	278	(592)	2,494	(2,225)
Provision for loan losses	616	6,268	(3,029)	9,265
Balance at End of Period	13,898	14,799	13,898	14,799
Commercial Construction [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	4,759	5,812	5,374	7,500
Charge-offs	(234)	(480)	(693)	(923)
Recoveries	0	481	140	536
Net (Charge-offs)/ Recoveries	(234)	1	(553)	(387)
Provision for loan losses	653	2,186	357	886
Balance at End of Period	5,178	7,999	5,178	7,999
Consumer Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	6,705	6,655	6,362	5,058
Charge-offs	(436)	(585)	(983)	(1,822)
Recoveries	48	122	272	630
Net (Charge-offs)/ Recoveries	(388)	(463)	(711)	(1,192)
Provision for loan losses	446	185	1,112	2,511
Balance at End of Period	6,763	6,377	6,763	6,377
Other Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	1,379	1,031	1,165	921
Charge-offs	(295)	(327)	(740)	(978)
Recoveries	75	63	284	242
Net (Charge-offs)/ Recoveries	(220)	(264)	(456)	(736)
Provision for loan losses	341	352	791	934
Balance at End of Period	$ 1,500	$ 1,119	$ 1,500	$ 1,119