Loans and Leases - Credit Quality Indicators (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012		Sep. 30, 2012
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	$ 1,526,241	$ 1,481,862	[1]	$ 1,469,511
Grade:1. Cash secured/2. Fully secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	8,079	2,263
Grade:3. Strong [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	18,941	18,725
Grade:4. Satisfactory [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	52,424	68,702
Grade:5. Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	682,798	630,331
Grade:6. Pre-watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	246,211	267,560
Grade:7. Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	39,985	48,848
Grade:8. Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	98,517	87,550
Grade:9. Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	413	993
Grade:10. Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment
Internally Assigned Grades [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	1,147,368	1,124,972
Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	376,876	355,202
Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	1,997	1,688
Performing and Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	378,873	356,890
Commercial, financial and agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	430,818	468,421		476,125
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	4,498	2,263
Commercial, financial and agricultural [Member] | Grade:3. Strong [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	5,534	5,227
Commercial, financial and agricultural [Member] | Grade:4. Satisfactory [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	33,136	40,747
Commercial, financial and agricultural [Member] | Grade:5. Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	246,455	260,042
Commercial, financial and agricultural [Member] | Grade:6. Pre-watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	98,524	106,436
Commercial, financial and agricultural [Member] | Grade:7. Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	15,897	31,825
Commercial, financial and agricultural [Member] | Grade:8. Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	26,410	21,881
Commercial, financial and agricultural [Member] | Grade:9. Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	364
Commercial, financial and agricultural [Member] | Grade:10. Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment
Commercial, financial and agricultural [Member] | Internally Assigned Grades [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	430,818	468,421
Real estate-commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	606,030	530,122
Real estate-commercial real estate [Member] | Grade:1. Cash secured/2. Fully secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	2,031
Real estate-commercial real estate [Member] | Grade:3. Strong [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	9,119	9,591
Real estate-commercial real estate [Member] | Grade:4. Satisfactory [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	17,579	25,837
Real estate-commercial real estate [Member] | Grade:5. Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	376,724	321,194
Real estate-commercial real estate [Member] | Grade:6. Pre-watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	121,054	110,476
Real estate-commercial real estate [Member] | Grade:7. Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	22,169	16,187
Real estate-commercial real estate [Member] | Grade:8. Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	57,305	45,844
Real estate-commercial real estate [Member] | Grade:9. Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	49	993
Real estate-commercial real estate [Member] | Grade:10. Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment
Real estate-commercial real estate [Member] | Internally Assigned Grades [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	606,030	530,122
Real estate-construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	74,847	91,250
Real estate-construction [Member] | Grade:1. Cash secured/2. Fully secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	1,550
Real estate-construction [Member] | Grade:3. Strong [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	4,288	3,907
Real estate-construction [Member] | Grade:4. Satisfactory [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	1,602	1,783
Real estate-construction [Member] | Grade:5. Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	33,898	26,331
Real estate-construction [Member] | Grade:6. Pre-watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	21,282	42,190
Real estate-construction [Member] | Grade:7. Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment		548
Real estate-construction [Member] | Grade:8. Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	12,227	16,491
Real estate-construction [Member] | Grade:9. Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment
Real estate-construction [Member] | Grade:10. Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment
Real estate-construction [Member] | Internally Assigned Grades [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	74,847	91,250
Real estate-residential secured for business purpose [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	35,673	35,179		32,820
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
Real estate-residential secured for business purpose [Member] | Grade:3. Strong [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment
Real estate-residential secured for business purpose [Member] | Grade:4. Satisfactory [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	107	335
Real estate-residential secured for business purpose [Member] | Grade:5. Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	25,721	22,764
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	5,351	8,458
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	1,919	288
Real estate-residential secured for business purpose [Member] | Grade:8. Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	2,575	3,334
Real estate-residential secured for business purpose [Member] | Grade:9. Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment
Real estate-residential secured for business purpose [Member] | Grade:10. Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment
Real estate-residential secured for business purpose [Member] | Internally Assigned Grades [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	35,673	35,179
Real estate-residential secured for personal purpose [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	143,374	146,526
Real estate-residential secured for personal purpose [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	142,035	145,722
Real estate-residential secured for personal purpose [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	1,339	804
Real estate-residential secured for personal purpose [Member] | Performing and Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	143,374	146,526
Real estate-home equity secured for personal purpose [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	90,527	82,727
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	90,476	82,673
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	51	54
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	90,527	82,727
Loans to individuals [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	42,211	43,780		42,626
Loans to individuals [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	41,875	43,395
Loans to individuals [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	336	385
Loans to individuals [Member] | Performing and Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	42,211	43,780
Lease financings [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	102,761	83,857		76,562
Lease financings [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	102,490	83,412
Lease financings [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	271	445
Lease financings [Member] | Performing and Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	$ 102,761	$ 83,857

[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.