Loans and Allowance for Loan Losses - Summary of Impaired Financial Receivables (Analysis of Covered Impaired Loans) (Detail) (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	$ 176,828	$ 244,344
Recorded Investment With No Allowance	134,906	179,883	88,322
Recorded Investment With Allowance
Total impaired loans	134,906	179,883	88,322
Related Allowance
Average Recorded Investment	163,825	138,950	44,184
Commercial, financial & agricultural [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Unpaid Contractual Principal Balance	15,888	21,352
Recorded Investment With No Allowance	10,802	12,027
Recorded Investment With Allowance
Total impaired loans	10,802	12,027
Related Allowance
Average Recorded Investment	12,506	10,210
Real estate - construction & development [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Unpaid Contractual Principal Balance	30,979	47,005
Recorded Investment With No Allowance	23,236	34,363
Recorded Investment With Allowance
Total impaired loans	23,236	34,363
Related Allowance
Average Recorded Investment	29,970	30,610
Real estate - commercial and farmland [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Unpaid Contractual Principal Balance	84,124	106,953
Recorded Investment With No Allowance	64,231	84,740
Recorded Investment With Allowance
Total impaired loans	64,231	84,740
Related Allowance
Average Recorded Investment	78,790	56,607
Real estate - residential [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Unpaid Contractual Principal Balance	45,464	68,411
Recorded Investment With No Allowance	36,335	48,280
Recorded Investment With Allowance
Total impaired loans	36,335	48,280
Related Allowance
Average Recorded Investment	42,061	40,675
Consumer installment loans [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Unpaid Contractual Principal Balance	373	623
Recorded Investment With No Allowance	302	473
Recorded Investment With Allowance
Total impaired loans	302	473
Related Allowance
Average Recorded Investment	$ 498	$ 848