Loans and Allowance for Loan Losses - Summary of Credit Quality Indicate Financial Receivable (Loan Excluding Purchased Non-Covered and Covered Loans Portfolio) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	$ 1,889,881	$ 1,618,454
Commercial, Financial & Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	319,654	244,373
Real Estate - Construction & Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	161,507	146,371
Commercial And Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	907,524	808,323
Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	456,106	351,886
Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	30,782	34,249
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	14,308	33,252
Excluding Purchased Non-Covered and Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	1,889,881	1,618,454
Excluding Purchased Non-Covered and Covered Loans [Member] | 10 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	128,577	74,381
Excluding Purchased Non-Covered and Covered Loans [Member] | 15 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	217,804	230,212
Excluding Purchased Non-Covered and Covered Loans [Member] | 20 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	947,948	773,051
Excluding Purchased Non-Covered and Covered Loans [Member] | 23 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	29,205	31,604
Excluding Purchased Non-Covered and Covered Loans [Member] | 25 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	488,187	420,491
Excluding Purchased Non-Covered and Covered Loans [Member] | 30 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	25,983	30,591
Excluding Purchased Non-Covered and Covered Loans [Member] | 40 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	52,176	57,987
Excluding Purchased Non-Covered and Covered Loans [Member] | 50 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	1	137
Excluding Purchased Non-Covered and Covered Loans [Member] | 60 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial & Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	319,654	244,373
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial & Agricultural [Member] | 10 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	121,355	66,983
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial & Agricultural [Member] | 15 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	25,318	24,789
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial & Agricultural [Member] | 20 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	100,599	93,852
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial & Agricultural [Member] | 23 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	56	127
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial & Agricultural [Member] | 25 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	62,519	50,373
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial & Agricultural [Member] | 30 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	3,758	2,111
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial & Agricultural [Member] | 40 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	6,049	6,011
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial & Agricultural [Member] | 50 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	127
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial, Financial & Agricultural [Member] | 60 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction & Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	161,507	146,371
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction & Development [Member] | 10 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	268	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction & Development [Member] | 15 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	4,010	4,655
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction & Development [Member] | 20 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	47,541	45,195
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction & Development [Member] | 23 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	8,933	8,343
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction & Development [Member] | 25 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	93,514	78,736
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction & Development [Member] | 30 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	1,474	2,876
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction & Development [Member] | 40 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	5,767	6,566
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction & Development [Member] | 50 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Construction & Development [Member] | 60 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial And Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	907,524	808,323
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial And Farmland [Member] | 10 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	155	265
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial And Farmland [Member] | 15 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	128,170	147,157
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial And Farmland [Member] | 20 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	511,198	431,790
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial And Farmland [Member] | 23 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	10,507	10,219
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial And Farmland [Member] | 25 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	224,464	181,645
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial And Farmland [Member] | 30 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	13,035	11,849
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial And Farmland [Member] | 40 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	19,995	25,398
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial And Farmland [Member] | 50 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Commercial And Farmland [Member] | 60 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	456,106	351,886
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member] | 10 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	226	419
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member] | 15 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	59,301	52,335
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member] | 20 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	256,758	150,343
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member] | 23 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	9,672	12,641
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member] | 25 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	102,998	103,427
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member] | 30 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	7,459	13,558
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member] | 40 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	19,692	19,153
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member] | 50 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	10
Excluding Purchased Non-Covered and Covered Loans [Member] | Real Estate - Residential [Member] | 60 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	30,782	34,249
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member] | 10 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	6,573	6,714
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member] | 15 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	1,005	1,276
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member] | 20 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	17,544	18,619
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member] | 23 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	37	274
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member] | 25 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	4,692	6,310
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member] | 30 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	257	197
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member] | 40 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	673	859
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member] | 50 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	1	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Consumer Installment Loans [Member] | 60 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	14,308	33,252
Excluding Purchased Non-Covered and Covered Loans [Member] | Other [Member] | 10 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Other [Member] | 15 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Other [Member] | 20 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	14,308	33,252
Excluding Purchased Non-Covered and Covered Loans [Member] | Other [Member] | 23 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Other [Member] | 25 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Other [Member] | 30 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Other [Member] | 40 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Other [Member] | 50 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	0	0
Excluding Purchased Non-Covered and Covered Loans [Member] | Other [Member] | 60 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans portfolio by risk grade	$ 0	$ 0