Loans and Leases - Reserve for Loan and Lease Losses Roll Forward (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 24,718	$ 30,502	$ 24,746	[1]	$ 29,870
Charge-offs	(4,194)	(5,832)	(10,359)		(11,560)
Recoveries	217	216	834		1,133
Provision (recovery of provision)	4,094	2,210	9,614		7,653
Ending balance	24,835	27,096	24,835		27,096
Commercial, financial and agricultural [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	11,395	12,021	11,594		11,262
Charge-offs	(812)	(4,143)	(1,973)		(7,308)
Recoveries	85	33	172		448
Provision (recovery of provision)	(152)	3,344	723		6,853
Ending balance	10,516	11,255	10,516		11,255
Real Estate-Commercial and Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	8,662	12,316	7,507		13,317
Charge-offs	(2,784)	(1,318)	(6,857)		(2,993)
Recoveries		4	48		144
Provision (recovery of provision)	2,542	(763)	7,722		(229)
Ending balance	8,420	10,239	8,420		10,239
Real estate-residential secured for business purpose [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	586	834	639		823
Charge-offs	(38)		(112)
Recoveries	1	4	9		59
Provision (recovery of provision)	682	(154)	695		(198)
Ending balance	1,231	684	1,231		684
Real Estate-Residential and Home Equity Secured for Personal Purpose [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,084	884	980		735
Charge-offs	(133)		(160)		(2)
Recoveries	2		5		3
Provision (recovery of provision)	249	62	377		210
Ending balance	1,202	946	1,202		946
Loans to individuals [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	693	719	679		730
Charge-offs	(216)	(168)	(620)		(408)
Recoveries	60	43	172		100
Provision (recovery of provision)	169	12	475		184
Ending balance	706	606	706		606
Lease financings [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,212	1,161	1,326		1,344
Charge-offs	(211)	(203)	(637)		(849)
Recoveries	69	132	428		379
Provision (recovery of provision)	198	94	151		310
Ending balance	1,268	1,184	1,268		1,184
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,086	2,567	2,021		1,659
Charge-offs
Recoveries
Provision (recovery of provision)	406	(385)	(529)		523
Ending balance	$ 1,492	$ 2,182	$ 1,492		$ 2,182

[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.