Loans and Leases - Age Analysis of Past Due Loans and Leases (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012		Jun. 30, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	$ 6,857	$ 7,003
60-89 Days Past Due	1,143	699
Greater Than 90 Days Past Due	521	441
Total Past Due	8,521	8,143
Current	1,452,569	1,428,130
Total Loans and Leases Held for Investment	1,499,993	1,481,862	[1]	1,465,449
Recorded Investment Greater than 90 Days Past Due and Accruing Interest	521	441
Commercial, financial and agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	949	416
60-89 Days Past Due	274	95
Greater Than 90 Days Past Due
Total Past Due	1,223	511
Current	435,538	464,588
Total Loans and Leases Held for Investment	439,907	468,421		497,955
Recorded Investment Greater than 90 Days Past Due and Accruing Interest
Real estate-commercial real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,391	1,173
60-89 Days Past Due
Greater Than 90 Days Past Due
Total Past Due	1,391	1,173
Current	560,112	504,086
Total Loans and Leases Held for Investment	580,400	530,122
Recorded Investment Greater than 90 Days Past Due and Accruing Interest
Real estate-construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due		306
60-89 Days Past Due
Greater Than 90 Days Past Due
Total Past Due		306
Current	68,453	74,959
Total Loans and Leases Held for Investment	84,027	91,250
Recorded Investment Greater than 90 Days Past Due and Accruing Interest
Real estate-residential secured for business purpose [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	353	1,663
60-89 Days Past Due	37
Greater Than 90 Days Past Due
Total Past Due	390	1,663
Current	31,770	33,344
Total Loans and Leases Held for Investment	32,329	35,179		32,097
Recorded Investment Greater than 90 Days Past Due and Accruing Interest
Real estate-residential secured for personal purpose [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	2,176	1,617
60-89 Days Past Due	155	152
Greater Than 90 Days Past Due	221
Total Past Due	2,552	1,769
Current	140,720	143,953
Total Loans and Leases Held for Investment	144,002	146,526
Recorded Investment Greater than 90 Days Past Due and Accruing Interest	221
Real estate-home equity secured for personal purpose [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	459	276
60-89 Days Past Due	77	64
Greater Than 90 Days Past Due	74	54
Total Past Due	610	394
Current	83,499	82,333
Total Loans and Leases Held for Investment	84,109	82,727
Recorded Investment Greater than 90 Days Past Due and Accruing Interest	74	54
Loans to individuals [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	519	551
60-89 Days Past Due	276	115
Greater Than 90 Days Past Due	190	347
Total Past Due	985	1,013
Current	42,575	42,729
Total Loans and Leases Held for Investment	43,598	43,780		44,037
Recorded Investment Greater than 90 Days Past Due and Accruing Interest	190	347
Lease financings [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,010	1,001
60-89 Days Past Due	324	273
Greater Than 90 Days Past Due	36	40
Total Past Due	1,370	1,314
Current	89,902	82,138
Total Loans and Leases Held for Investment	91,621	83,857		75,255
Recorded Investment Greater than 90 Days Past Due and Accruing Interest	$ 36	$ 40

[1] Note: The consolidated balance sheet at December 31, 2012 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by U. S. generally accepted accounting principles for complete financial statements. See accompanying notes to the unaudited consolidated financial statements.