Loans and Allowance for Loan Losses - Summary of Non-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
Purchased Non-Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	10,347	12,903
Loans 60-89 Days Past Due	4,420	3,314
Loans 90 or More Days Past Due	17,255	5,289
Total Loans Past Due	32,022	21,506
Current Loans	642,217	427,247
Total Loans	674,239	448,753
Loans 90 Days or More Past Due and Still Accruing	0	0
Purchased Non-Covered Loans [Member] | Commercial, Financial & Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	461	370
Loans 60-89 Days Past Due	90	70
Loans 90 or More Days Past Due	175	11
Total Loans Past Due	726	451
Current Loans	37,315	31,690
Total Loans	38,041	32,141
Loans 90 Days or More Past Due and Still Accruing	0	0
Purchased Non-Covered Loans [Member] | Real Estate - Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	790	1,008
Loans 60-89 Days Past Due	1,735	89
Loans 90 or More Days Past Due	1,117	325
Total Loans Past Due	3,642	1,422
Current Loans	54,720	29,754
Total Loans	58,362	31,176
Loans 90 Days or More Past Due and Still Accruing	0	0
Purchased Non-Covered Loans [Member] | Commercial And Farmland [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	2,107	6,851
Loans 60-89 Days Past Due	1,194	2,064
Loans 90 or More Days Past Due	9,529	1,516
Total Loans Past Due	12,830	10,431
Current Loans	293,876	169,467
Total Loans	306,706	179,898
Loans 90 Days or More Past Due and Still Accruing	0	0
Purchased Non-Covered Loans [Member] | Real Estate - Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	6,907	4,667
Loans 60-89 Days Past Due	1,401	1,074
Loans 90 or More Days Past Due	6,369	3,428
Total Loans Past Due	14,677	9,169
Current Loans	251,665	191,682
Total Loans	266,342	200,851
Loans 90 Days or More Past Due and Still Accruing	0	0
Purchased Non-Covered Loans [Member] | Consumer Installment Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	82	7
Loans 60-89 Days Past Due		17
Loans 90 or More Days Past Due	65	9
Total Loans Past Due	147	33
Current Loans	4,641	4,654
Total Loans	4,788	4,687
Loans 90 Days or More Past Due and Still Accruing	$ 0	$ 0