Loans - Summary of Impaired Financial Receivables (Analysis of Covered Impaired Loans) (Detail) (Covered Loans [Member], USD $) In Thousands, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	$ 138,035	$ 239,122	$ 335,784
Recorded Investment With No Allowance	111,648	166,067	134,906
Recorded Investment With Allowance
Total impaired loans	111,648	166,067	134,906
Related Allowance
Average Recorded Investment	122,220	178,130	163,825
Commercial, Financial and Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	12,150	22,616	27,060
Recorded Investment With No Allowance	8,769	13,464	10,802
Recorded Investment With Allowance
Total impaired loans	8,769	13,464	10,802
Related Allowance
Average Recorded Investment	9,442	13,250	12,506
Real Estate - Construction and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	28,494	46,439	85,279
Recorded Investment With No Allowance	22,830	30,586	23,236
Recorded Investment With Allowance
Total impaired loans	22,830	30,586	23,236
Related Allowance
Average Recorded Investment	23,348	34,260	29,970
Real Estate - Commercial and Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	65,516	110,388	159,493
Recorded Investment With No Allowance	53,837	81,330	64,231
Recorded Investment With Allowance
Total impaired loans	53,837	81,330	64,231
Related Allowance
Average Recorded Investment	57,962	85,639	78,790
Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	31,535	58,645	63,559
Recorded Investment With No Allowance	25,927	40,033	36,335
Recorded Investment With Allowance
Total impaired loans	25,927	40,033	36,335
Related Allowance
Average Recorded Investment	31,191	44,393	42,061
Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	340	1,034	393
Recorded Investment With No Allowance	285	654	302
Recorded Investment With Allowance
Total impaired loans	285	654	302
Related Allowance
Average Recorded Investment	$ 277	$ 588	$ 498