Loans and Leases - Credit Quality Indicators (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	$ 1,597,736	$ 1,541,484	$ 1,526,241
Grade: 1. Cash secured/ 2. Fully secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	5,362	8,459
Grade: 3. Strong [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	19,935	18,866
Grade: 4. Satisfactory [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	64,118	54,169
Grade: 5. Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	784,244	716,422
Grade: 6. Pre-watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	180,727	219,350
Grade: 7. Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	23,512	31,381
Grade: 8. Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	109,183	101,941
Grade: 9. Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	0	393
Grade: 10. Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	0	0
Internally Assigned Grades [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	1,187,081	1,150,981
Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	409,421	388,558
Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	1,234	1,945
Performing and Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	410,655	390,503
Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	438,556	422,816	430,818
Commercial, Financial and Agricultural [Member] | Grade: 1. Cash secured/ 2. Fully secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	4,511	4,763
Commercial, Financial and Agricultural [Member] | Grade: 3. Strong [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	7,187	6,051
Commercial, Financial and Agricultural [Member] | Grade: 4. Satisfactory [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	26,274	34,650
Commercial, Financial and Agricultural [Member] | Grade: 5. Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	291,646	251,203
Commercial, Financial and Agricultural [Member] | Grade: 6. Pre-watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	56,775	84,201
Commercial, Financial and Agricultural [Member] | Grade: 7. Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	11,904	10,095
Commercial, Financial and Agricultural [Member] | Grade: 8. Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	40,259	31,508
Commercial, Financial and Agricultural [Member] | Grade: 9. Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	0	345
Commercial, Financial and Agricultural [Member] | Grade: 10. Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	0	0
Commercial, Financial and Agricultural [Member] | Internally Assigned Grades [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	438,556	422,816
Real Estate-Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	637,904	600,353
Real Estate-Commercial [Member] | Grade: 1. Cash secured/ 2. Fully secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	0	2,014
Real Estate-Commercial [Member] | Grade: 3. Strong [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	8,821	8,515
Real Estate-Commercial [Member] | Grade: 4. Satisfactory [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	28,667	17,758
Real Estate-Commercial [Member] | Grade: 5. Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	419,615	384,061
Real Estate-Commercial [Member] | Grade: 6. Pre-watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	113,842	113,181
Real Estate-Commercial [Member] | Grade: 7. Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	10,283	19,445
Real Estate-Commercial [Member] | Grade: 8. Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	56,676	55,331
Real Estate-Commercial [Member] | Grade: 9. Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	0	48
Real Estate-Commercial [Member] | Grade: 10. Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	0	0
Real Estate-Commercial [Member] | Internally Assigned Grades [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	637,904	600,353
Real Estate-Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	75,254	90,493
Real Estate-Construction [Member] | Grade: 1. Cash secured/ 2. Fully secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	851	1,682
Real Estate-Construction [Member] | Grade: 3. Strong [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	3,927	4,300
Real Estate-Construction [Member] | Grade: 4. Satisfactory [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	8,834	1,500
Real Estate-Construction [Member] | Grade: 5. Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	48,889	54,464
Real Estate-Construction [Member] | Grade: 6. Pre-watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	5,088	16,084
Real Estate-Construction [Member] | Grade: 7. Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	0	0
Real Estate-Construction [Member] | Grade: 8. Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	7,665	12,463
Real Estate-Construction [Member] | Grade: 9. Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	0	0
Real Estate-Construction [Member] | Grade: 10. Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	0	0
Real Estate-Construction [Member] | Internally Assigned Grades [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	75,254	90,493
Real Estate-Residential Secured for Business Purpose [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	35,367	37,319	35,673
Real Estate-Residential Secured for Business Purpose [Member] | Grade: 1. Cash secured/ 2. Fully secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	0	0
Real Estate-Residential Secured for Business Purpose [Member] | Grade: 3. Strong [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	0	0
Real Estate-Residential Secured for Business Purpose [Member] | Grade: 4. Satisfactory [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	343	261
Real Estate-Residential Secured for Business Purpose [Member] | Grade: 5. Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	24,094	26,694
Real Estate-Residential Secured for Business Purpose [Member] | Grade: 6. Pre-watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	5,022	5,884
Real Estate-Residential Secured for Business Purpose [Member] | Grade: 7. Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	1,325	1,841
Real Estate-Residential Secured for Business Purpose [Member] | Grade: 8. Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	4,583	2,639
Real Estate-Residential Secured for Business Purpose [Member] | Grade: 9. Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	0	0
Real Estate-Residential Secured for Business Purpose [Member] | Grade: 10. Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	0	0
Real Estate-Residential Secured for Business Purpose [Member] | Internally Assigned Grades [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	35,367	37,319
Real Estate-Residential Secured for Personal Purpose [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	163,368	149,164
Real Estate-Residential Secured for Personal Purpose [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	162,801	148,063
Real Estate-Residential Secured for Personal Purpose [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	567	1,101
Real Estate-Residential Secured for Personal Purpose [Member] | Performing and Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	163,368	149,164
Real Estate-Home Equity Secured for Personal Purpose [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	105,191	95,345
Real Estate-Home Equity Secured for Personal Purpose [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	105,114	95,245
Real Estate-Home Equity Secured for Personal Purpose [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	77	100
Real Estate-Home Equity Secured for Personal Purpose [Member] | Performing and Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	105,191	95,345
Loans to Individuals [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	30,144	40,000	42,211
Loans to Individuals [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	29,887	39,645
Loans to Individuals [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	257	355
Loans to Individuals [Member] | Performing and Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	30,144	40,000
Lease Financings [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	111,952	105,994	102,761
Lease Financings [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	111,619	105,605
Lease Financings [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	333	389
Lease Financings [Member] | Performing and Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	$ 111,952	$ 105,994