Loans and Allowance for Loan Losses - Summary of Financial Receivable Nonaccrual Basis (Detail) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Finance Receivable Transferred To Held For Sale [Line Items]
Covered loans		$ 200,000
Non-Covered Loan [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Covered loans	38,885,000	70,823,000	79,289,000	96,131,000	65,414,000
Non-Covered Loan [Member] | Commercial, financial & agricultural [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Covered loans	4,138,000	3,987,000	8,648,000	4,774,000	4,810,000
Non-Covered Loan [Member] | Real estate - construction & development [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Covered loans	9,281,000	15,020,000	7,887,000	15,787,000	10,522,000
Non-Covered Loan [Member] | Real estate - commercial and farmland [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Covered loans	11,962,000	35,385,000	55,170,000	67,172,000	44,235,000
Non-Covered Loan [Member] | Real estate - residential [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Covered loans	12,595,000	15,498,000	6,376,000	6,965,000	4,730,000
Non-Covered Loan [Member] | Consumer installment loans [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Covered loans	909,000	933,000	1,208,000	1,433,000	1,117,000
Covered Loan [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Covered loans	115,712,000	159,999,000	88,153,000	25,791,000
Covered Loan [Member] | Commercial, financial & agricultural [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Covered loans	10,765,000	11,952,000	5,756,000	1,398,000
Covered Loan [Member] | Real estate - construction & development [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Covered loans	20,027,000	30,977,000	25,810,000	9,155,000
Covered Loan [Member] | Real estate - commercial and farmland [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Covered loans	55,946,000	75,458,000	29,519,000	8,109,000
Covered Loan [Member] | Real estate - residential [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Covered loans	28,672,000	41,139,000	25,946,000	4,602,000
Covered Loan [Member] | Consumer installment loans [Member]
Finance Receivable Transferred To Held For Sale [Line Items]
Covered loans	$ 302,000	$ 473,000	$ 1,122,000	$ 2,527,000