Loans - Summary of Covered Past Due Financial Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Accounts, Notes, Loans and Financing Receivable [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]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	334,917	319,654	270,571
Real Estate - Construction & Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	178,568	161,507	149,543
Commercial And Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	947,274	907,524	836,230
Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	496,043	456,106	393,001
Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	29,113	30,782	32,345
Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans 30-59 Days Past Due	5,277	8,534	24,249
Loans 60-89 Days Past Due	2,394	2,810	5,714
Loans 90 or More Days Past Due	23,530	22,039	50,983
Total Loans Past Due	31,201	33,383	80,946
Current Loans	214,544	237,896	291,748
Total Loans	245,745	271,279	372,694
Loans 90 Days or More Past Due and Still Accruing		714	1,396
Covered Loans [Member] | Commercial, Financial & Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans 30-59 Days Past Due	165	451	688
Loans 60-89 Days Past Due	225	136	55
Loans 90 or More Days Past Due	1,776	1,878	8,976
Total Loans Past Due	2,166	2,465	9,719
Current Loans	18,739	19,002	15,094
Total Loans	20,905	21,467	24,813
Covered Loans [Member] | Real Estate - Construction & Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans 30-59 Days Past Due	455	238	4,248
Loans 60-89 Days Past Due		226	302
Loans 90 or More Days Past Due	5,605	6,703	14,472
Total Loans Past Due	6,060	7,167	19,022
Current Loans	13,459	16,280	22,412
Total Loans	19,519	23,447	41,434
Covered Loans [Member] | Commercial And Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans 30-59 Days Past Due	2,364	4,371	15,732
Loans 60-89 Days Past Due	1,150	1,486	3,722
Loans 90 or More Days Past Due	11,063	7,711	17,680
Total Loans Past Due	14,577	13,568	37,134
Current Loans	115,713	134,059	177,515
Total Loans	130,290	147,627	214,649
Loans 90 Days or More Past Due and Still Accruing		714
Covered Loans [Member] | Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans 30-59 Days Past Due	2,293	3,464	3,579
Loans 60-89 Days Past Due	1,019	962	1,585
Loans 90 or More Days Past Due	4,999	5,656	9,752
Total Loans Past Due	8,310	10,082	14,916
Current Loans	66,536	68,438	76,456
Total Loans	74,847	78,520	91,372
Loans 90 Days or More Past Due and Still Accruing			1,396
Covered Loans [Member] | Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans 30-59 Days Past Due		10	2
Loans 60-89 Days Past Due			50
Loans 90 or More Days Past Due	87	91	103
Total Loans Past Due	87	101	155
Current Loans	97	117	271
Total Loans	$ 184	$ 218	$ 426