Loans - Summary of Impaired Financial Receivables (Analysis of Non-Covered Impaired Loans) (Detail) (Non-Covered Loan [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	$ 65,594	$ 79,403	$ 78,758
Recorded Investment With No Allowance
Recorded Investment With Allowance	48,744	58,118	57,629
Total impaired loans	48,744	58,118	57,629
Related Allowance	5,180	7,681	5,115
Average Recorded Investment	53,047	73,353	70,209
Commercial, Financial and Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	7,401	8,261	8,024
Recorded Investment With No Allowance
Recorded Investment With Allowance	4,719	5,089	4,940
Total impaired loans	4,719	5,089	4,940
Related Allowance	820	876	743
Average Recorded Investment	4,900	4,974	4,968
Real Estate - Construction and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	14,299	19,583	20,316
Recorded Investment With No Allowance
Recorded Investment With Allowance	6,155	9,682	11,016
Total impaired loans	6,155	9,682	11,016
Related Allowance	821	1,253	910
Average Recorded Investment	8,960	11,879	11,706
Real Estate - Commercial and Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	18,628	25,346	25,076
Recorded Investment With No Allowance
Recorded Investment With Allowance	16,241	20,948	20,910
Total impaired loans	16,241	20,948	20,910
Related Allowance	1,999	2,907	2,191
Average Recorded Investment	18,079	33,070	30,638
Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	24,701	24,993	24,155
Recorded Investment With No Allowance
Recorded Investment With Allowance	21,174	21,304	19,848
Total impaired loans	21,174	21,304	19,848
Related Allowance	1,530	2,616	1,246
Average Recorded Investment	20,427	22,303	21,813
Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Contractual Principal Balance	565	1,220	1,187
Recorded Investment With No Allowance
Recorded Investment With Allowance	455	1,095	915
Total impaired loans	455	1,095	915
Related Allowance	10	29	25
Average Recorded Investment	$ 681	$ 1,127	$ 1,084