Loans and Leases - Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Impaired loans, with no related allowance, Recorded Investment	$ 37,912	$ 44,508
Impaired loans, with no related allowance, Unpaid Principal Balance	50,911	54,497
Impaired loans with an allowance recorded, Recorded Investment	642	676
Impaired loans, with an allowance recorded, Unpaid Principal Balance	702	717
Total impaired loans, Recorded Investment	38,554	45,184
Total impaired loans, Unpaid Principal Balance	51,613	55,214
Total impaired loans, Related Allowance	230	208
Commercial, financial and agricultural [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans, with no related allowance, Recorded Investment	2,504	2,646
Impaired loans, with no related allowance, Unpaid Principal Balance	4,082	4,504
Impaired loans with an allowance recorded, Recorded Investment	642	676
Impaired loans, with an allowance recorded, Unpaid Principal Balance	702	717
Total impaired loans, Recorded Investment	3,146	3,322
Total impaired loans, Unpaid Principal Balance	4,784	5,221
Total impaired loans, Related Allowance	230	208
Real estate-commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans, with no related allowance, Recorded Investment	18,897	24,863
Impaired loans, with no related allowance, Unpaid Principal Balance	28,269	30,991
Total impaired loans, Recorded Investment	18,897	24,863
Total impaired loans, Unpaid Principal Balance	28,269	30,991
Total impaired loans, Related Allowance
Real estate-construction [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans, with no related allowance, Recorded Investment	15,574	15,985
Impaired loans, with no related allowance, Unpaid Principal Balance	17,594	17,959
Total impaired loans, Recorded Investment	15,574	15,985
Total impaired loans, Unpaid Principal Balance	17,594	17,959
Total impaired loans, Related Allowance
Real estate-residential secured for business purpose [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans, with no related allowance, Recorded Investment	169	172
Impaired loans, with no related allowance, Unpaid Principal Balance	181	184
Total impaired loans, Recorded Investment	169	172
Total impaired loans, Unpaid Principal Balance	181	184
Total impaired loans, Related Allowance
Real estate-residential secured for personal purpose [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans, with no related allowance, Recorded Investment	730	804
Impaired loans, with no related allowance, Unpaid Principal Balance	730	804
Total impaired loans, Recorded Investment	730	804
Total impaired loans, Unpaid Principal Balance	730	804
Total impaired loans, Related Allowance
Loans to individuals [Member]
Financing Receivable, Impaired [Line Items]
Impaired loans, with no related allowance, Recorded Investment	38	38
Impaired loans, with no related allowance, Unpaid Principal Balance	55	55
Total impaired loans, Recorded Investment	38	38
Total impaired loans, Unpaid Principal Balance	55	55
Total impaired loans, Related Allowance