Loans and Allowance for Loan Losses - Summary of Covered Loans According to Loan Type (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	$ 507,712	$ 571,489
Commercial, financial & agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	32,606	41,867
Real estate - construction & development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	70,184	77,077
Real estate - commercial and farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	278,506	321,257
Real estate - residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	125,056	127,644
Consumer installment loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	$ 1,360	$ 3,644