Loans - Schedule of Accounts Notes Loans and Financial Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	$ 1,848,759	$ 1,618,454	$ 1,589,267
Commercial, Financial and Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	334,783	244,373	244,991
Real Estate - Construction and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	154,315	146,371	132,277
Real Estate - Commercial and Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	882,160	808,323	799,149
Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	436,515	366,882	355,920
Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	31,403	34,249	36,303
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	$ 9,583	$ 18,256	$ 20,627