Loans - Schedule of Allowances for Loan Losses by Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Loans Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 22,377	$ 23,593	$ 23,593
Provision for loan losses	1,501	2,603	9,947
Loans charged off	(1,606)	(3,036)	(13,284)
Ending balance	22,744	23,382	22,377
Recoveries of loans previously charged off	472	222	2,121
Ending balance	22,744	23,382	22,377
Period-End Amount Allocated to [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	4,076	4,409	3,585
Loans collectively evaluated for impairment	18,668	18,973	18,792
Ending balance	22,744	23,382	22,377
Ending balance	22,744	23,382	22,377
Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	38,088	45,229	39,203
Collectively evaluated for impairment	1,657,294	1,447,524	1,579,251
Ending balance	1,695,382	1,492,753	1,618,454
Commercial, Financial and Agricultural [Member] | Loans Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,823	2,439	2,439
Provision for loan losses	1,090	254	711
Loans charged off	(743)	(410)	(1,759)
Ending balance	2,219	2,367	1,823
Recoveries of loans previously charged off	49	84	432
Ending balance	2,219	2,367	1,823
Commercial, Financial and Agricultural [Member] | Period-End Amount Allocated to [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	318	675	356
Loans collectively evaluated for impairment	1,901	1,692	1,467
Ending balance	2,219	2,367	1,823
Ending balance	2,219	2,367	1,823
Commercial, Financial and Agricultural [Member] | Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	2,837	3,334	3,457
Collectively evaluated for impairment	267,734	177,554	240,916
Ending balance	270,571	180,888	244,373
Real Estate - Construction and Development [Member] | Loans Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	5,538	5,343	5,343
Provision for loan losses	337	1,467	1,742
Loans charged off	(65)	(655)	(2,020)
Ending balance	5,918	6,157	5,538
Recoveries of loans previously charged off	108	2	473
Ending balance	5,918	6,157	5,538
Real Estate - Construction and Development [Member] | Period-End Amount Allocated to [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	631	641	407
Loans collectively evaluated for impairment	5,287	5,516	5,131
Ending balance	5,918	6,157	5,538
Ending balance	5,918	6,157	5,538
Real Estate - Construction and Development [Member] | Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	3,817	8,281	3,581
Collectively evaluated for impairment	145,726	121,880	142,790
Ending balance	149,543	130,161	146,371
Real Estate - Commercial and Farmland [Member] | Loans Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	8,393	9,157	9,157
Provision for loan losses	622	696	2,777
Loans charged off	(533)	(1,025)	(3,571)
Ending balance	8,625	8,831	8,393
Recoveries of loans previously charged off	143	3	30
Ending balance	8,625	8,831	8,393
Real Estate - Commercial and Farmland [Member] | Period-End Amount Allocated to [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	1,994	1,890	1,427
Loans collectively evaluated for impairment	6,631	6,941	6,966
Ending balance	8,625	8,831	8,393
Ending balance	8,625	8,831	8,393
Real Estate - Commercial and Farmland [Member] | Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	16,832	19,545	15,240
Collectively evaluated for impairment	819,398	746,682	793,083
Ending balance	836,230	766,227	808,323
Real Estate - Residential [Member] | Loans Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	6,034	5,898	5,898
Provision for loan losses	(656)	339	4,463
Loans charged off	(181)	(779)	(5,215)
Ending balance	5,280	5,543	6,034
Recoveries of loans previously charged off	83	85	888
Ending balance	5,280	5,543	6,034
Real Estate - Residential [Member] | Period-End Amount Allocated to [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	1,133	1,203	1,395
Loans collectively evaluated for impairment	4,147	4,340	4,639
Ending balance	5,280	5,543	6,034
Ending balance	5,280	5,543	6,034
Real Estate - Residential [Member] | Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually evaluated for impairment	14,602	14,069	16,925
Collectively evaluated for impairment	378,399	352,987	349,957
Ending balance	393,001	367,056	366,882
Consumer Installment Loans and Other [Member] | Loans Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	589	756	756
Provision for loan losses	108	(153)	254
Loans charged off	(84)	(167)	(719)
Ending balance	702	484	589
Recoveries of loans previously charged off	89	48	298
Ending balance	702	484	589
Consumer Installment Loans and Other [Member] | Period-End Amount Allocated to [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans collectively evaluated for impairment	702	484	589
Ending balance	702	484	589
Ending balance	702	484	589
Consumer Installment Loans and Other [Member] | Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Collectively evaluated for impairment	46,037	48,421	52,505
Ending balance	$ 46,037	$ 48,421	$ 52,505