Loans and Leases - Age Analysis of Past Due Loans and Leases (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	$ 14,564	$ 4,896
60-89 Days Past Due	3,878	2,205
90 Days or more Past Due	8,469	18,164
Total Past Due	26,911	25,265
Current	1,570,825	1,516,219
Total Loans and Leases Held for Investment	1,597,736	1,541,484	1,526,241
Recorded Investment 90 Days or more Past Due and Accruing Interest	344	413
Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,380	386
60-89 Days Past Due	872	922
90 Days or more Past Due	588	2,904
Total Past Due	2,840	4,212
Current	435,716	418,604
Total Loans and Leases Held for Investment	438,556	422,816	430,818
Recorded Investment 90 Days or more Past Due and Accruing Interest	0	12
Real Estate-Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	9,630	148
60-89 Days Past Due	0	262
90 Days or more Past Due	148	4,932
Total Past Due	9,778	5,342
Current	628,126	595,011
Total Loans and Leases Held for Investment	637,904	600,353
Recorded Investment 90 Days or more Past Due and Accruing Interest	0	0
Real Estate-Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	405	0
60-89 Days Past Due	0	0
90 Days or more Past Due	6,297	8,742
Total Past Due	6,702	8,742
Current	68,552	81,751
Total Loans and Leases Held for Investment	75,254	90,493
Recorded Investment 90 Days or more Past Due and Accruing Interest	0	0
Real Estate-Residential Secured for Business Purpose [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	224	87
60-89 Days Past Due	18	276
90 Days or more Past Due	668	161
Total Past Due	910	524
Current	34,457	36,795
Total Loans and Leases Held for Investment	35,367	37,319	35,673
Recorded Investment 90 Days or more Past Due and Accruing Interest	0	0
Real Estate-Residential Secured for Personal Purpose [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	377	1,370
60-89 Days Past Due	424	0
90 Days or more Past Due	101	617
Total Past Due	902	1,987
Current	162,466	147,177
Total Loans and Leases Held for Investment	163,368	149,164
Recorded Investment 90 Days or more Past Due and Accruing Interest	41	0
Real Estate-Home Equity Secured for Personal Purpose [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	336	278
60-89 Days Past Due	127	97
90 Days or more Past Due	77	100
Total Past Due	540	475
Current	104,651	94,870
Total Loans and Leases Held for Investment	105,191	95,345
Recorded Investment 90 Days or more Past Due and Accruing Interest	0	23
Loans to Individuals [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	294	445
60-89 Days Past Due	219	193
90 Days or more Past Due	257	319
Total Past Due	770	957
Current	29,374	39,043
Total Loans and Leases Held for Investment	30,144	40,000	42,211
Recorded Investment 90 Days or more Past Due and Accruing Interest	257	319
Lease Financings [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,918	2,182
60-89 Days Past Due	2,218	455
90 Days or more Past Due	333	389
Total Past Due	4,469	3,026
Current	107,483	102,968
Total Loans and Leases Held for Investment	111,952	105,994	102,761
Recorded Investment 90 Days or more Past Due and Accruing Interest	$ 46	$ 59