Loans - Summary of Covered Loans According to Loan Type (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	$ 460,724	$ 507,712	$ 653,377
Commercial, financial & agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	28,568	32,606	43,157
Real estate - construction & development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	57,114	70,184	93,430
Real estate - commercial & farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	260,159	278,506	350,244
Real estate - residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	113,668	125,056	162,768
Consumer installment loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	$ 1,215	$ 1,360	$ 3,778