Loans and Allowance for Loan Losses - Summary of Covered Past Due Financial Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans 30-59 Days Past Due	$ 29,100	$ 30,400
Total Loans	1,889,881	1,618,454
Commercial, Financial & Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	319,654	244,373
Real Estate - Construction & Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	161,507	146,371
Commercial And Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	907,524	808,323
Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	456,106	351,886
Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	30,782	34,249
Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans 30-59 Days Past Due	8,534	20,990
Loans 60-89 Days Past Due	2,810	6,434
Loans 90 or More Days Past Due	22,039	57,197
Total Loans Past Due	33,383	84,621
Current Loans	237,896	305,616
Total Loans	271,279	390,237
Loans 90 Days or More Past Due and Still Accruing	714	346
Covered Loans [Member] | Commercial, Financial & Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans 30-59 Days Past Due	451	3,966
Loans 60-89 Days Past Due	136	12
Loans 90 or More Days Past Due	1,878	6,165
Total Loans Past Due	2,465	10,143
Current Loans	19,002	16,407
Total Loans	21,467	26,550
Loans 90 Days or More Past Due and Still Accruing	0	0
Covered Loans [Member] | Real Estate - Construction & Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans 30-59 Days Past Due	238	843
Loans 60-89 Days Past Due	226	144
Loans 90 or More Days Past Due	6,703	14,055
Total Loans Past Due	7,167	15,042
Current Loans	16,280	28,137
Total Loans	23,447	43,179
Loans 90 Days or More Past Due and Still Accruing	0	0
Covered Loans [Member] | Commercial And Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans 30-59 Days Past Due	4,371	8,482
Loans 60-89 Days Past Due	1,486	4,350
Loans 90 or More Days Past Due	7,711	26,428
Total Loans Past Due	13,568	39,260
Current Loans	134,059	185,191
Total Loans	147,627	224,451
Loans 90 Days or More Past Due and Still Accruing	714	346
Covered Loans [Member] | Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans 30-59 Days Past Due	3,464	7,648
Loans 60-89 Days Past Due	962	1,914
Loans 90 or More Days Past Due	5,656	10,244
Total Loans Past Due	10,082	19,806
Current Loans	68,438	75,367
Total Loans	78,520	95,173
Loans 90 Days or More Past Due and Still Accruing	0	0
Covered Loans [Member] | Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans 30-59 Days Past Due	10	51
Loans 60-89 Days Past Due	0	14
Loans 90 or More Days Past Due	91	305
Total Loans Past Due	101	370
Current Loans	117	514
Total Loans	218	884
Loans 90 Days or More Past Due and Still Accruing	$ 0	$ 0