Loans - Summary of Excluding Purchased Non-Covered and Covered Past Due Financial Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	$ 32,000		$ 6,300
Total Loans	1,999,420	1,889,881	1,695,382
Commercial, Financial & Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	334,917	319,654	270,571
Real Estate - Construction & Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	178,568	161,507	149,543
Commercial And Farmland [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	947,274	907,524	836,230
Real Estate - Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	496,043	456,106	393,001
Consumer Installment Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	29,113	30,782	32,345
Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	13,505	14,308	13,692
Excluding Purchased Non-Covered and Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	12,857	9,728	8,773
Loans 60-89 Days Past Due	6,361	3,646	3,894
Loans 90 or More Days Past Due	19,746	19,733	25,140
Total Loans Past Due	38,964	33,107	37,807
Current Loans	1,960,456	1,856,774	1,657,575
Total Loans	1,999,420	1,889,881	1,695,382
Loans 90 Days or More Past Due and Still Accruing		1
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	1,258	900	1,083
Loans 60-89 Days Past Due	2,821	233	386
Loans 90 or More Days Past Due	984	1,577	2,956
Total Loans Past Due	5,063	2,710	4,425
Current Loans	329,854	316,944	266,146
Total Loans	334,917	319,654	270,571
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	404	1,382	1,304
Loans 60-89 Days Past Due	240	286	249
Loans 90 or More Days Past Due	3,205	3,367	3,919
Total Loans Past Due	3,849	5,035	5,472
Current Loans	174,719	156,472	144,071
Total Loans	178,568	161,507	149,543
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	6,398	2,859	2,255
Loans 60-89 Days Past Due	1,285	635	1,650
Loans 90 or More Days Past Due	7,732	7,668	7,622
Total Loans Past Due	15,415	11,162	11,527
Current Loans	931,859	896,362	824,703
Total Loans	947,274	907,524	836,230
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	4,430	3,953	3,657
Loans 60-89 Days Past Due	1,879	2,334	1,541
Loans 90 or More Days Past Due	7,569	6,755	10,298
Total Loans Past Due	13,878	13,042	15,496
Current Loans	482,165	443,064	377,505
Total Loans	496,043	456,106	393,001
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	367	634	474
Loans 60-89 Days Past Due	136	158	68
Loans 90 or More Days Past Due	256	366	345
Total Loans Past Due	759	1,158	887
Current Loans	28,354	29,624	31,458
Total Loans	29,113	30,782	32,345
Loans 90 Days or More Past Due and Still Accruing		1
Excluding Purchased Non-Covered and Covered Loans [Member] | Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	13,505	14,308	13,692
Total Loans	$ 13,505	$ 14,308	$ 13,692