Loans - Summary of Trouble Debt Restructuring by Loan Class (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Financing Receivable, Modifications [Line Items]
Troubled debt restructuring loans	$ 20,600	$ 23,900	$ 28,200
Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	61	55	45
Troubled debt restructuring loans	18,015	18,744	22,970
Accruing Loans [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	7	5
Troubled debt restructuring loans	1,059	802
Accruing Loans [Member] | Real Estate - Construction and Development [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	7	5	5
Troubled debt restructuring loans	1,946	1,735	1,205
Accruing Loans [Member] | Real Estate - Commercial and Farmland [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	16	16	16
Troubled debt restructuring loans	7,529	8,947	13,293
Accruing Loans [Member] | Real Estate - Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	30	28	24
Troubled debt restructuring loans	7,468	7,254	8,472
Accruing Loans [Member] | Consumer Installment Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	1
Troubled debt restructuring loans	13	6
Non-Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	9	5	10
Troubled debt restructuring loans	2,568	5,171	5,170
Non-Accruing Loans [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts			1
Troubled debt restructuring loans			18
Non-Accruing Loans [Member] | Real Estate - Construction and Development [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1		2
Troubled debt restructuring loans	29		1,124
Non-Accruing Loans [Member] | Real Estate - Commercial and Farmland [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2	3	2
Troubled debt restructuring loans	1,493	4,149	2,815
Non-Accruing Loans [Member] | Real Estate - Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	6	2	5
Troubled debt restructuring loans	$ 1,046	$ 1,022	$ 1,213
Non-Accruing Loans [Member] | Consumer Installment Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	0