Loans - Activity in Allowance for Loan Losses by Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	$ 93,589	$ 107,181	$ 104,453	$ 110,147
Provision for loan losses	3,575	2,355	9,575	3,455
Charge-offs	(6,534)	(7,662)	(26,465)	(15,790)
Recoveries	2,770	3,774	5,837	7,836
Net charge-offs	(3,764)	(3,888)	(20,628)	(7,954)
Ending balance	93,400	105,648	93,400	105,648
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	51,085	45,869	54,164	42,774
Provision for loan losses	2,612	10,786	16,060	15,552
Charge-offs	(3,586)	(4,474)	(20,738)	(7,486)
Recoveries	703	1,294	1,328	2,635
Net charge-offs	(2,883)	(3,180)	(19,410)	(4,851)
Ending balance	50,814	53,475	50,814	53,475
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	24,809	20,003	29,346	20,912
Provision for loan losses	(1,108)	7,123	(5,974)	8,564
Charge-offs	(415)	(353)	(681)	(3,195)
Recoveries	287	858	882	1,350
Net charge-offs	(128)	505	201	(1,845)
Ending balance	23,573	27,631	23,573	27,631
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	5,148	3,699	5,252	3,540
Provision for loan losses	(246)	2,055	(74)	1,980
Charge-offs	(159)	(606)	(495)	(895)
Recoveries	174	87	234	610
Net charge-offs	15	(519)	(261)	(285)
Ending balance	4,917	5,235	4,917	5,235
Consumer and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	3,724	8,715	3,507	12,635
Provision for loan losses	1,174	(4,372)	1,781	(8,013)
Charge-offs	(2,374)	(2,229)	(4,551)	(4,214)
Recoveries	1,606	1,535	3,393	3,241
Net charge-offs	(768)	(694)	(1,158)	(973)
Ending balance	4,130	3,649	4,130	3,649
Unallocated [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	8,823	28,895	12,184	30,286
Provision for loan losses	1,143	(13,237)	(2,218)	(14,628)
Charge-offs
Recoveries
Net charge-offs
Ending balance	$ 9,966	$ 15,658	$ 9,966	$ 15,658