Loans - Summary of Excluding Purchased Non-Covered and Covered Past Due Financial Receivables (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 2,171,600	$ 1,889,881	$ 1,770,059
Loans 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	54,800		8,400
Commercial, Financial & Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	373,202	319,654	304,588
Real Estate - Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	205,019	161,507	149,346
Real Estate - Commercial & Farmland [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,010,195	907,524	850,000
Real Estate - Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	537,201	456,106	422,731
Consumer Installment Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	30,080	30,782	31,902
Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	15,903	14,308	11,492
Excluding Purchased Non-Covered and Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	33,021	33,107	42,459
Current Loans	2,138,579	1,856,774	1,727,600
Total Loans	2,171,600	1,889,881	1,770,059
Loans 90 Days or More Past Due and Still Accruing		1
Excluding Purchased Non-Covered and Covered Loans [Member] | Loans 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	9,427	9,728	15,895
Excluding Purchased Non-Covered and Covered Loans [Member] | Loans 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	6,111	3,646	7,127
Excluding Purchased Non-Covered and Covered Loans [Member] | Loans 90 or More Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	17,483	19,733	19,437
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial & Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	5,619	2,710	3,223
Current Loans	367,583	316,944	301,365
Total Loans	373,202	319,654	304,588
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial & Agricultural [Member] | Loans 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	840	900	1,180
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial & Agricultural [Member] | Loans 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	888	233	966
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial & Agricultural [Member] | Loans 90 or More Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	3,891	1,577	1,077
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	3,111	5,035	7,687
Current Loans	201,908	156,472	141,659
Total Loans	205,019	161,507	149,346
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction & Development [Member] | Loans 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	1,201	1,382	3,942
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction & Development [Member] | Loans 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	374	286	296
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction & Development [Member] | Loans 90 or More Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	1,536	3,367	3,449
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Commercial & Farmland [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	11,795	11,162	13,886
Current Loans	998,400	896,362	836,114
Total Loans	1,010,195	907,524	850,000
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Commercial & Farmland [Member] | Loans 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	1,958	2,859	4,622
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Commercial & Farmland [Member] | Loans 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	2,823	635	1,860
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Commercial & Farmland [Member] | Loans 90 or More Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	7,014	7,668	7,404
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	11,811	13,042	16,832
Current Loans	525,390	443,064	405,899
Total Loans	537,201	456,106	422,731
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member] | Loans 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	5,135	3,953	5,806
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member] | Loans 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	1,949	2,334	3,829
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member] | Loans 90 or More Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	4,727	6,755	7,197
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	685	1,158	831
Current Loans	29,395	29,624	31,071
Total Loans	30,080	30,782	31,902
Loans 90 Days or More Past Due and Still Accruing		1
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member] | Loans 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	293	634	345
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member] | Loans 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	77	158	176
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member] | Loans 90 or More Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Past Due	315	366	310
Excluding Purchased Non-Covered and Covered Loans [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	15,903	14,308	11,492
Total Loans	$ 15,903	$ 14,308	$ 11,492