Loans and Leases - Reserve for Loan and Lease Losses Roll Forward (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
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 25,222	$ 30,597	$ 24,746	[1]	$ 29,870
Charge-offs	(4,319)	(2,022)	(6,165)		(5,728)
Recoveries	369	584	617		917
Provision (recovery of provision)	3,446	1,343	5,520		5,443
Ending balance	24,718	30,502	24,718		30,502
Commercial, financial and agricultural [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	11,883	11,701	11,594		11,262
Charge-offs	(90)	(1,458)	(1,161)		(3,165)
Recoveries	39	362	87		415
Provision (recovery of provision)	(437)	1,416	875		3,509
Ending balance	11,395	12,021	11,395		12,021
Real estate-commercial and construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	8,032	13,352	7,507		13,317
Charge-offs	(3,691)	(133)	(4,073)		(1,675)
Recoveries	42	44	48		140
Provision (recovery of provision)	4,279	(947)	5,180		534
Ending balance	8,662	12,316	8,662		12,316
Real estate-residential secured for business purpose [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	570	948	639		823
Charge-offs	(24)		(74)
Recoveries		3	8		55
Provision (recovery of provision)	40	(117)	13		(44)
Ending balance	586	834	586		834
Real estate-residential and home equity secured for personal purpose [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	792	732	980		735
Charge-offs	(23)	(2)	(27)		(2)
Recoveries	1	1	3		3
Provision (recovery of provision)	314	153	128		148
Ending balance	1,084	884	1,084		884
Loans to individuals [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	628	704	679		730
Charge-offs	(224)	(119)	(404)		(240)
Recoveries	78	26	112		57
Provision (recovery of provision)	211	108	306		172
Ending balance	693	719	693		719
Lease financings [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,358	1,160	1,326		1,344
Charge-offs	(267)	(310)	(426)		(646)
Recoveries	209	148	359		247
Provision (recovery of provision)	(88)	163	(47)		216
Ending balance	1,212	1,161	1,212		1,161
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,959	2,000	2,021		1,659
Charge-offs
Recoveries
Provision (recovery of provision)	(873)	567	(935)		908
Ending balance	$ 1,086	$ 2,567	$ 1,086		$ 2,567

[1] Note: The consolidated balance sheet at December 31, 2012 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by U. S. generally accepted accounting principles for complete financial statements. See accompanying notes to the unaudited consolidated financial statements.