Loans - Summary of Non-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
Purchased Non-Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-59 Days Past Due	5,433	10,347	10,126
Loans 60-89 Days Past Due	3,302	4,420	7,614
Loans 90 or More Days Past Due	15,855	17,255	10,067
Total Loans Past Due	24,590	32,022	27,807
Current Loans	618,502	642,217	409,462
Total Loans	643,092	674,239	437,269
Loans 90 Days or More Past Due and Still Accruing	0	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	216	461	291
Loans 60-89 Days Past Due		90
Loans 90 or More Days Past Due	85	175	117
Total Loans Past Due	301	726	408
Current Loans	35,957	37,315	30,402
Total Loans	36,258	38,041	30,810
Loans 90 Days or More Past Due and Still Accruing	0	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	393	790	680
Loans 60-89 Days Past Due	17	1,735	661
Loans 90 or More Days Past Due	766	1,117	867
Total Loans Past Due	1,176	3,642	2,208
Current Loans	52,492	54,720	29,612
Total Loans	53,668	58,362	31,820
Loans 90 Days or More Past Due and Still Accruing	0	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	1,611	2,107	3,956
Loans 60-89 Days Past Due	831	1,194	5,126
Loans 90 or More Days Past Due	8,495	9,529	2,550
Total Loans Past Due	10,937	12,830	11,632
Current Loans	280,823	293,876	162,649
Total Loans	291,760	306,706	174,281
Loans 90 Days or More Past Due and Still Accruing	0	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	3,113	6,907	5,187
Loans 60-89 Days Past Due	2,454	1,401	1,816
Loans 90 or More Days Past Due	6,490	6,369	6,503
Total Loans Past Due	12,057	14,677	13,506
Current Loans	245,159	251,665	182,572
Total Loans	257,216	266,342	196,078
Loans 90 Days or More Past Due and Still Accruing	0	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	100	82	12
Loans 60-89 Days Past Due			11
Loans 90 or More Days Past Due	19	65	30
Total Loans Past Due	119	147	53
Current Loans	4,071	4,641	4,227
Total Loans	4,190	4,788	4,280
Loans 90 Days or More Past Due and Still Accruing	$ 0	$ 0	$ 0