Loans and Allowance for Loan Losses - Schedule of Accounts Notes Loans and Financial Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	$ 1,889,881	$ 1,618,454
Allowance for loan losses	21,157	22,377
Loans, net	1,868,724	1,596,077
Commercial, Financial & Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	319,654	244,373
Real Estate - Construction & Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	161,507	146,371
Commercial And Farmland [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	907,524	808,323
Real Estate - Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	456,106	351,886
Consumer Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	30,782	34,249
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and deferred loan fees receivables	$ 14,308	$ 33,252