Loans - Summary of Covered Loans According to Loan Type (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	$ 417,649	$ 507,712	$ 546,234
Commercial, Financial and Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	27,768	32,606	37,167
Real Estate - Construction and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	50,702	70,184	73,356
Real Estate - Commercial and Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	237,086	278,506	298,903
Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	101,146	125,056	135,154
Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	$ 947	$ 1,360	$ 1,654