Loans - Summary of Troubled Debt Restructuring by Loan Class, Classified Separately Under Terms (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013 Contract	Dec. 31, 2012 Contract	Jun. 30, 2012 Contract
Loans Currently Paying Under Restructured Terms [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	62	54	50
Troubled debt restructuring loans	$ 18,335	$ 18,738	$ 26,960
Loans Currently Paying Under Restructured Terms [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	7	5	1
Troubled debt restructuring loans	1,059	802	18
Loans Currently Paying Under Restructured Terms [Member] | Real Estate - Construction and Development [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	7	5	6
Troubled debt restructuring loans	1,946	1,735	2,305
Loans Currently Paying Under Restructured Terms [Member] | Real Estate - Commercial and Farmland [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	16	16	18
Troubled debt restructuring loans	7,529	8,947	16,108
Loans Currently Paying Under Restructured Terms [Member] | Real Estate - Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	31	28	25
Troubled debt restructuring loans	7,788	7,254	8,529
Loans Currently Paying Under Restructured Terms [Member] | Consumer Installment Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1
Troubled debt restructuring loans	13
Loans that have Defaulted Under Restructured Terms [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	8	6	5
Troubled debt restructuring loans	2,248	5,177	1,180
Loans that have Defaulted Under Restructured Terms [Member] | Real Estate - Construction and Development [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1		1
Troubled debt restructuring loans	29		24
Loans that have Defaulted Under Restructured Terms [Member] | Real Estate - Commercial and Farmland [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2	3
Troubled debt restructuring loans	1,493	4,149
Loans that have Defaulted Under Restructured Terms [Member] | Real Estate - Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	5	2	4
Troubled debt restructuring loans	726	1,022	1,156
Loans that have Defaulted Under Restructured Terms [Member] | Consumer Installment Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts		1
Troubled debt restructuring loans		$ 6