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, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 24,094	$ 24,718	$ 24,494	$ 24,746
Charge-offs	(2,857)	(4,194)	(6,838)	(10,359)
Recoveries	292	217	1,147	834
Provision (recovery of provision)	233	4,094	2,959	9,614
Ending balance	21,762	24,835	21,762	24,835
Commercial, Financial and Agricultural [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	9,714	11,395	9,789	11,594
Charge-offs	(968)	(812)	(2,657)	(1,973)
Recoveries	88	85	197	172
Provision (recovery of provision)	(1,219)	(152)	286	723
Ending balance	7,615	10,516	7,615	10,516
Real Estate-Commercial and Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	9,263	8,662	8,780	7,507
Charge-offs	(1,570)	(2,784)	(2,878)	(6,857)
Recoveries	58	0	428	48
Provision (recovery of provision)	1,337	2,542	2,758	7,722
Ending balance	9,088	8,420	9,088	8,420
Real Estate-Residential Secured for Business Purpose [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,025	586	1,062	639
Charge-offs	(26)	(38)	(140)	(112)
Recoveries	9	1	57	9
Provision (recovery of provision)	(48)	682	(19)	695
Ending balance	960	1,231	960	1,231
Real Estate-Residential and Home Equity Secured for Personal Purpose [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,248	1,084	1,284	980
Charge-offs	(18)	(133)	(108)	(160)
Recoveries	2	2	29	5
Provision (recovery of provision)	(54)	249	(27)	377
Ending balance	1,178	1,202	1,178	1,202
Loans to Individuals [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	405	693	694	679
Charge-offs	(169)	(216)	(659)	(620)
Recoveries	53	60	212	172
Provision (recovery of provision)	43	169	85	475
Ending balance	332	706	332	706
Lease Financings [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,101	1,212	1,285	1,326
Charge-offs	(106)	(211)	(396)	(637)
Recoveries	82	69	224	428
Provision (recovery of provision)	38	198	2	151
Ending balance	1,115	1,268	1,115	1,268
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,338	1,086	1,600	2,021
Provision (recovery of provision)	136	406	(126)	(529)
Ending balance	$ 1,474	$ 1,492	$ 1,474	$ 1,492