Loans - Schedule of Accounts Notes Loans and Financial Receivables (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	$ 2,171,600	$ 1,889,881	$ 1,770,059
Commercial, Financial & Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	373,202	319,654	304,588
Real Estate - Construction & Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	205,019	161,507	149,346
Real Estate - Commercial & Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	1,010,195	907,524	850,000
Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	537,201	456,106	422,731
Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	30,080	30,782	31,902
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	$ 15,903	$ 14,308	$ 11,492