Loans and Allowance for Loan Losses - Summary of Carrying Value of Covered Loans According to Loan Type (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered Loans	$ 271,279	$ 390,237
Commercial, Financial & Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered Loans	21,467	26,550
Real Estate - Construction & Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered Loans	23,447	43,179
Commercial And Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered Loans	147,627	224,451
Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered Loans	78,520	95,173
Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered Loans	$ 218	$ 884