Loans and Leases - Credit Quality Indicators (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	$ 1,626,625	$ 1,541,484
Grade: 1. Cash secured/ 2. Fully secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	5,510	8,459
Grade: 3. Strong [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	26,414	18,866
Grade: 4. Satisfactory [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	63,588	54,169
Grade: 5. Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	783,790	716,422
Grade: 6. Pre-watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	199,462	219,350
Grade: 7. Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	25,975	31,381
Grade: 8. Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	98,385	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	1,203,124	1,150,981
Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	421,974	388,558
Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	1,527	1,945
Performing and Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	423,501	390,503
Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	457,827	422,816
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	4,248	4,763
Commercial, Financial and Agricultural [Member] | Grade: 3. Strong [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	14,013	6,051
Commercial, Financial and Agricultural [Member] | Grade: 4. Satisfactory [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	23,931	34,650
Commercial, Financial and Agricultural [Member] | Grade: 5. Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	301,425	251,203
Commercial, Financial and Agricultural [Member] | Grade: 6. Pre-watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	65,993	84,201
Commercial, Financial and Agricultural [Member] | Grade: 7. Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	7,166	10,095
Commercial, Financial and Agricultural [Member] | Grade: 8. Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	41,051	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	457,827	422,816
Real Estate-Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	628,478	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	8,504	8,515
Real Estate-Commercial [Member] | Grade: 4. Satisfactory [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	30,587	17,758
Real Estate-Commercial [Member] | Grade: 5. Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	402,719	384,061
Real Estate-Commercial [Member] | Grade: 6. Pre-watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	123,129	113,181
Real Estate-Commercial [Member] | Grade: 7. Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	17,505	19,445
Real Estate-Commercial [Member] | Grade: 8. Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	46,034	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	628,478	600,353
Real Estate-Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	79,887	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	1,262	1,682
Real Estate-Construction [Member] | Grade: 3. Strong [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	3,897	4,300
Real Estate-Construction [Member] | Grade: 4. Satisfactory [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	8,731	1,500
Real Estate-Construction [Member] | Grade: 5. Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	55,111	54,464
Real Estate-Construction [Member] | Grade: 6. Pre-watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	4,956	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	5,930	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	79,887	90,493
Real Estate-Residential Secured for Business Purpose [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	36,932	37,319
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	339	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	24,535	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	5,384	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	1,304	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	5,370	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	36,932	37,319
Real Estate-Residential Secured for Personal Purpose [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	166,850	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	166,338	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	512	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	166,850	149,164
Real Estate-Home Equity Secured for Personal Purpose [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	108,250	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	108,035	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	215	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	108,250	95,345
Loans to Individuals [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	29,941	40,000
Loans to Individuals [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	29,576	39,645
Loans to Individuals [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	365	355
Loans to Individuals [Member] | Performing and Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	29,941	40,000
Lease Financings [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	118,460	105,994
Lease Financings [Member] | Performing Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	118,025	105,605
Lease Financings [Member] | Nonperforming Financing Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	435	389
Lease Financings [Member] | Performing and Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases held for investment	$ 118,460	$ 105,994