Loans - Summary of Impaired Financial Receivables (Analysis of Non-Covered Impaired Loans) (Detail) (Non-Covered Loan [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	$ 66,987	$ 87,586	$ 78,758
Recorded Investment With No Allowance
Recorded Investment With Allowance	49,826	67,391	57,629
Total Recorded Investment	49,826	67,391	57,629
Related Allowance	5,072	7,136	5,115
Average Recorded Investment	54,481	78,432	70,209
Commercial, Financial and Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	7,723	8,116	8,024
Recorded Investment With No Allowance
Recorded Investment With Allowance	5,384	4,968	4,940
Total Recorded Investment	5,384	4,968	4,940
Related Allowance	1,018	692	743
Average Recorded Investment	4,960	4,936	4,968
Real Estate - Construction and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	15,324	18,805	20,316
Recorded Investment With No Allowance
Recorded Investment With Allowance	7,394	10,184	11,016
Total Recorded Investment	7,394	10,184	11,016
Related Allowance	687	1,070	910
Average Recorded Investment	9,894	12,611	11,706
Real Estate - Commercial and Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	19,759	32,265	25,076
Recorded Investment With No Allowance
Recorded Investment With Allowance	16,491	27,021	20,910
Total Recorded Investment	16,491	27,021	20,910
Related Allowance	1,657	2,081	2,191
Average Recorded Investment	18,692	37,111	30,638
Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	23,373	27,069	24,155
Recorded Investment With No Allowance
Recorded Investment With Allowance	19,893	24,014	19,848
Total Recorded Investment	19,893	24,014	19,848
Related Allowance	1,692	3,254	1,246
Average Recorded Investment	20,178	22,637	21,813
Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	808	1,331	1,187
Recorded Investment With No Allowance
Recorded Investment With Allowance	664	1,204	915
Total Recorded Investment	664	1,204	915
Related Allowance	18	39	25
Average Recorded Investment	$ 757	$ 1,137	$ 1,084