Loans and Allowance for Loan Losses - Summary of Impaired Financial Receivables (Analysis of Non-Covered Impaired Loans) (Detail) (Non-Covered Loan [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Finance Receivable Transferred To Held For Sale [Line Items]
Unpaid Contractual Principal Balance	$ 78,758	$ 106,538
Recorded Investment With No Allowance
Recorded Investment With Allowance	57,629	88,774	101,261
Total Recorded Investment	57,629	88,774	101,261
Related Allowance	5,115	18,478	16,688
Average Recorded Investment	70,209	88,320	103,776
Commercial, financial & agricultural [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Unpaid Contractual Principal Balance	8,024	9,592
Recorded Investment With No Allowance
Recorded Investment With Allowance	4,940	5,110
Total Recorded Investment	4,940	5,110
Related Allowance	743	1,366
Average Recorded Investment	4,968	5,700
Real estate - construction & development [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Unpaid Contractual Principal Balance	20,316	21,893
Recorded Investment With No Allowance
Recorded Investment With Allowance	11,016	15,672
Total Recorded Investment	11,016	15,672
Related Allowance	910	4,053
Average Recorded Investment	11,706	18,667
Real estate - commercial and farmland [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Unpaid Contractual Principal Balance	25,076	48,688
Recorded Investment With No Allowance
Recorded Investment With Allowance	20,910	45,006
Total Recorded Investment	20,910	45,006
Related Allowance	2,191	8,331
Average Recorded Investment	30,638	42,192
Real estate - residential [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Unpaid Contractual Principal Balance	24,155	25,309
Recorded Investment With No Allowance
Recorded Investment With Allowance	19,848	22,053
Total Recorded Investment	19,848	22,053
Related Allowance	1,246	4,499
Average Recorded Investment	21,813	21,081
Consumer installment loans [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Unpaid Contractual Principal Balance	1,187	1,056
Recorded Investment With No Allowance
Recorded Investment With Allowance	915	933
Total Recorded Investment	915	933
Related Allowance	25	229
Average Recorded Investment	$ 1,084	$ 680