Loans and Allowance for Loan Losses - Schedule of Allowances for Loan Losses By Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Loans Receivable [Member]
Beginning balance	$ 35,156	$ 34,576	$ 35,762
Provision for loan losses	28,451	30,341	48,839
Loans charged off	(41,163)	(31,623)	(52,623)
Recoveries of loans previously charged off	1,149	1,862	2,598
Ending balance	23,593	35,156	34,576
Period-end amount allocated to: [Member]
Loans individually evaluated for impairment	4,554	15,966	13,085
Loans collectively evaluated for impairment	19,039	19,190	21,491
Ending balance	23,593	35,156	34,576
Loans: [Member]
Individually evaluated for impairment	45,320	77,573	91,687
Collectively evaluated for impairment	1,405,315	1,254,513	1,283,070
Ending balance	1,450,635	1,332,086	1,374,757
Commercial, financial & agricultural [Member] | Loans Receivable [Member]
Beginning balance	2,918	2,779	3,428
Provision for loan losses	815	5,772	4,265
Loans charged off	(1,451)	(5,807)	(5,481)
Recoveries of loans previously charged off	157	174	567
Ending balance	2,439	2,918	2,779
Commercial, financial & agricultural [Member] | Period-end amount allocated to: [Member]
Loans individually evaluated for impairment	659	766	677
Loans collectively evaluated for impairment	1,780	2,152	2,102
Ending balance	2,439	2,918	2,779
Commercial, financial & agricultural [Member] | Loans: [Member]
Individually evaluated for impairment	3,351	2,831	3,930
Collectively evaluated for impairment	170,866	140,129	138,382
Ending balance	174,217	142,960	142,312
Real estate - construction & development [Member] | Loans Receivable [Member]
Beginning balance	9,438	7,705	13,098
Provision for loan losses	5,245	11,354	13,776
Loans charged off	(9,380)	(10,988)	(19,853)
Recoveries of loans previously charged off	40	1,367	684
Ending balance	5,343	9,438	7,705
Real estate - construction & development [Member] | Period-end amount allocated to: [Member]
Loans individually evaluated for impairment	611	3,478	3,554
Loans collectively evaluated for impairment	4,732	5,960	4,151
Ending balance	5,343	9,438	7,705
Real estate - construction & development [Member] | Loans: [Member]
Individually evaluated for impairment	7,617	13,561	22,838
Collectively evaluated for impairment	106,582	116,709	139,756
Ending balance	114,199	130,270	162,594
Real estate - commercial and farmland [Member] | Loans Receivable [Member]
Beginning balance	14,226	14,971	11,296
Provision for loan losses	15,000	7,883	18,937
Loans charged off	(20,551)	(8,680)	(16,108)
Recoveries of loans previously charged off	482	52	846
Ending balance	9,157	14,226	14,971
Real estate - commercial and farmland [Member] | Period-end amount allocated to: [Member]
Loans individually evaluated for impairment	2,228	8,152	6,300
Loans collectively evaluated for impairment	6,929	6,074	8,671
Ending balance	9,157	14,226	14,971
Real estate - commercial and farmland [Member] | Loans: [Member]
Individually evaluated for impairment	21,332	45,084	50,179
Collectively evaluated for impairment	710,990	627,681	633,795
Ending balance	732,322	672,765	683,974
Real estate - residential [Member] | Loans Receivable [Member]
Beginning balance	8,128	8,664	7,391
Provision for loan losses	6,267	4,717	11,178
Loans charged off	(8,722)	(5,399)	(10,091)
Recoveries of loans previously charged off	225	146	186
Ending balance	5,898	8,128	8,664
Real estate - residential [Member] | Period-end amount allocated to: [Member]
Loans individually evaluated for impairment	1,056	3,567	2,554
Loans collectively evaluated for impairment	4,842	4,561	6,110
Ending balance	5,898	8,128	8,664
Real estate - residential [Member] | Loans: [Member]
Individually evaluated for impairment	13,020	16,080	14,740
Collectively evaluated for impairment	333,460	314,647	330,090
Ending balance	346,480	330,727	344,830
Consumer Installment and Other [Member] | Loans Receivable [Member]
Beginning balance	446	457	549
Provision for loan losses	1,124	615	683
Loans charged off	(1,059)	(749)	(1,090)
Recoveries of loans previously charged off	245	123	315
Ending balance	756	446	457
Consumer Installment and Other [Member] | Period-end amount allocated to: [Member]
Loans individually evaluated for impairment		3
Loans collectively evaluated for impairment	756	443	457
Ending balance	756	446	457
Consumer Installment and Other [Member] | Loans: [Member]
Individually evaluated for impairment		17
Collectively evaluated for impairment	83,417	55,347	41,047
Ending balance	$ 83,417	$ 55,364	$ 41,047