Loans - Summary of Covered Loans According to Loan Type (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered Loans	$ 245,745	$ 271,279	$ 372,694
Commercial, Financial & Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered Loans	20,905	21,467	24,813
Real Estate - Construction & Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered Loans	19,519	23,447	41,434
Commercial And Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered Loans	130,290	147,627	214,649
Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered Loans	74,847	78,520	91,372
Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered Loans	$ 184	$ 218	$ 426