Loans and Allowance for Credit Losses - Schedule of Activity in Troubled Debt Restructurings (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Financing Receivable, Impaired [Line Items]
Beginning balance	$ 32,054	$ 12,990
(Charge-offs)/recoveries	1,052	(2,177)
Payments	(10,688)	(4,604)
Additions	24,062	22,616
Ending balance	46,480	28,825
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Beginning balance	12,660	7,086
(Charge-offs)/recoveries	639	(1,381)
Payments	(5,122)	(1,314)
Additions	13,238	5,556
Ending balance	21,415	9,947
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Beginning balance	18,422	5,851
(Charge-offs)/recoveries	474	(796)
Payments	(5,119)	(3,245)
Additions	8,961	16,426
Ending balance	22,738	18,236
Consumer Loan [Member]
Financing Receivable, Impaired [Line Items]
Beginning balance	473	53
(Charge-offs)/recoveries	(61)
Payments	(408)	(13)
Additions	836	266
Ending balance	840	306
Residential [Member]
Financing Receivable, Impaired [Line Items]
Beginning balance	499
Payments	(39)	(32)
Additions	1,027	368
Ending balance	$ 1,487	$ 336