Loans and Allowance for Loan Losses - Summary of Excluding Purchased Non-Covered and Covered Past Due Financial Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	$ 29,100	$ 30,400
Total Loans	1,889,881	1,618,454
Commercial, Financial & Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	319,654	244,373
Real Estate - Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	161,507	146,371
Commercial And Farmland [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	907,524	808,323
Real Estate - Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	456,106	351,886
Consumer Installment Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	30,782	34,249
Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	14,308	33,252
Excluding Purchased Non-Covered and Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	9,728	21,890
Loans 60-89 Days Past Due	3,646	3,661
Loans 90 or More Days Past Due	19,733	27,659
Total Loans Past Due	33,107	53,210
Current Loans	1,856,774	1,565,244
Total Loans	1,889,881	1,618,454
Loans 90 Days or More Past Due and Still Accruing	1	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial & Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	900	10,893
Loans 60-89 Days Past Due	233	272
Loans 90 or More Days Past Due	1,577	4,081
Total Loans Past Due	2,710	15,246
Current Loans	316,944	229,127
Total Loans	319,654	244,373
Loans 90 Days or More Past Due and Still Accruing		0
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	1,382	1,026
Loans 60-89 Days Past Due	286	69
Loans 90 or More Days Past Due	3,367	3,935
Total Loans Past Due	5,035	5,030
Current Loans	156,472	141,341
Total Loans	161,507	146,371
Loans 90 Days or More Past Due and Still Accruing		0
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial And Farmland [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	2,859	3,981
Loans 60-89 Days Past Due	635	1,388
Loans 90 or More Days Past Due	7,668	7,751
Total Loans Past Due	11,162	13,120
Current Loans	896,362	795,203
Total Loans	907,524	808,323
Loans 90 Days or More Past Due and Still Accruing		0
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	3,953	5,422
Loans 60-89 Days Past Due	2,334	1,735
Loans 90 or More Days Past Due	6,755	11,587
Total Loans Past Due	13,042	18,744
Current Loans	443,064	333,142
Total Loans	456,106	351,886
Loans 90 Days or More Past Due and Still Accruing		0
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	634	568
Loans 60-89 Days Past Due	158	197
Loans 90 or More Days Past Due	366	305
Total Loans Past Due	1,158	1,070
Current Loans	29,624	33,179
Total Loans	30,782	34,249
Loans 90 Days or More Past Due and Still Accruing	1	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due		0
Loans 60-89 Days Past Due		0
Loans 90 or More Days Past Due		0
Total Loans Past Due		0
Current Loans	14,308	33,252
Total Loans	14,308	33,252
Loans 90 Days or More Past Due and Still Accruing		$ 0