Loans - Summary of Impaired Financial Receivables (Analysis of Covered Impaired Loans) (Detail) (Covered Loans [Member], USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	$ 115,633	$ 206,439	$ 335,784
Recorded Investment With No Allowance	96,095	149,827	134,906
Recorded Investment With Allowance
Total impaired loans	96,095	149,827	134,906
Related Allowance
Average Recorded Investment	115,689	171,055	163,825
Commercial, Financial and Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	10,645	17,833	27,060
Recorded Investment With No Allowance	7,884	11,976	10,802
Recorded Investment With Allowance
Total impaired loans	7,884	11,976	10,802
Related Allowance
Average Recorded Investment	9,052	12,932	12,506
Real Estate - Construction and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	25,401	34,787	85,279
Recorded Investment With No Allowance	20,890	23,833	23,236
Recorded Investment With Allowance
Total impaired loans	20,890	23,833	23,236
Related Allowance
Average Recorded Investment	22,734	31,653	29,970
Real Estate - Commercial and Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	51,105	98,909	159,493
Recorded Investment With No Allowance	43,279	72,802	64,231
Recorded Investment With Allowance
Total impaired loans	43,279	72,802	64,231
Related Allowance
Average Recorded Investment	54,292	82,430	78,790
Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	28,078	54,020	63,559
Recorded Investment With No Allowance	23,692	40,790	36,335
Recorded Investment With Allowance
Total impaired loans	23,692	40,790	36,335
Related Allowance
Average Recorded Investment	29,316	43,492	42,061
Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	404	890	393
Recorded Investment With No Allowance	350	426	302
Recorded Investment With Allowance
Total impaired loans	350	426	302
Related Allowance
Average Recorded Investment	$ 295	$ 548	$ 498