Loans and Leases - Summary of Major Loan and Lease Categories (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, net of deferred income	$ 1,626,625	$ 1,541,484
Unearned lease income, included in the above table	(14,131)	(14,439)
Net deferred costs, included in the above table	3,218	2,744
Overdraft deposits included in the above table	50	62
Commercial, Financial and Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, net of deferred income	457,827	422,816
Real Estate-Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, net of deferred income	628,478	600,353
Real Estate-Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, net of deferred income	79,887	90,493
Real Estate-Residential Secured for Business Purpose [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, net of deferred income	36,932	37,319
Real Estate-Residential Secured for Personal Purpose [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, net of deferred income	166,850	149,164
Real Estate-Home Equity Secured for Personal Purpose [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, net of deferred income	108,250	95,345
Loans to Individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, net of deferred income	29,941	40,000
Lease Financings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, net of deferred income	$ 118,460	$ 105,994