Loans and Leases - Summary of Major Loan and Lease Categories (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, net of deferred income	$ 1,597,736	$ 1,541,484	$ 1,526,241
Unearned lease income, included in the above table	(13,646)	(14,439)
Net deferred costs, included in the above table	3,045	2,744
Overdraft deposits included in the above table	72	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	438,556	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	637,904	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	75,254	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	35,367	37,319	35,673
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	163,368	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	105,191	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	30,144	40,000	42,211
Lease Financings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, net of deferred income	$ 111,952	$ 105,994	$ 102,761