Loans - Summary of Financial Receivable Nonaccrual Basis (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	$ 200,000
Non-Covered Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	31,720,000	38,885,000	38,225,000
Non-Covered Loan [Member] | Commercial, Financial and Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	4,198,000	4,138,000	4,285,000
Non-Covered Loan [Member] | Real Estate - Construction and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	4,229,000	9,281,000	8,201,000
Non-Covered Loan [Member] | Real Estate - Commercial and Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	9,548,000	11,962,000	11,408,000
Non-Covered Loan [Member] | Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	13,303,000	12,595,000	13,236,000
Non-Covered Loan [Member] | Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	442,000	909,000	1,095,000
Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	74,911,000	115,712,000	123,901,000
Covered Loans [Member] | Commercial, Financial and Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	7,872,000	10,765,000	11,938,000
Covered Loans [Member] | Real Estate - Construction and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	16,582,000	20,027,000	21,971,000
Covered Loans [Member] | Real Estate - Commercial and Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	37,079,000	55,946,000	58,377,000
Covered Loans [Member] | Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	13,028,000	28,672,000	31,189,000
Covered Loans [Member] | Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	$ 350,000	$ 302,000	$ 426,000