Loans - Summary of Financial Receivable Nonaccrual Basis (Detail) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 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	37,476,000	38,885,000	52,258,000
Non-Covered Loan [Member] | Commercial, financial & agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	3,756,000	4,138,000	4,732,000
Non-Covered Loan [Member] | Real estate - construction & development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	9,390,000	9,281,000	10,647,000
Non-Covered Loan [Member] | Real estate - commercial & farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	9,798,000	11,962,000	21,539,000
Non-Covered Loan [Member] | Real estate - residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	13,840,000	12,595,000	14,065,000
Non-Covered Loan [Member] | Consumer installment loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	692,000	909,000	1,275,000
Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	98,515,000	115,712,000	170,221,000
Covered Loans [Member] | Commercial, financial & agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	8,718,000	10,765,000	14,185,000
Covered Loans [Member] | Real estate - construction & development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	18,956,000	20,027,000	35,170,000
Covered Loans [Member] | Real estate - commercial & farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	47,580,000	55,946,000	79,620,000
Covered Loans [Member] | Real estate - residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	23,018,000	28,672,000	40,609,000
Covered Loans [Member] | Consumer installment loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	$ 243,000	$ 302,000	$ 637,000