Loans and Leases - Nonaccrual and accruing troubled debt restructured loans and lease modifications (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Nonaccrual And Accruing Troubled Debt Restructured Loans And Lease Modifications [Line Items]
Nonaccrual Loans and Leases	$ 25,207	$ 32,132
Accruing Troubled Debt Restructured Loans and Lease Modifications	13,696	13,457
Total Impaired Loans and Leases	38,903	45,589
Commercial, financial and agricultural [Member]
Nonaccrual And Accruing Troubled Debt Restructured Loans And Lease Modifications [Line Items]
Nonaccrual Loans and Leases	1,708	2,842
Accruing Troubled Debt Restructured Loans and Lease Modifications	1,438	480
Total Impaired Loans and Leases	3,146	3,322
Real estate-commercial real estate [Member]
Nonaccrual And Accruing Troubled Debt Restructured Loans And Lease Modifications [Line Items]
Nonaccrual Loans and Leases	8,726	14,340
Accruing Troubled Debt Restructured Loans and Lease Modifications	10,171	10,523
Total Impaired Loans and Leases	18,897	24,863
Real estate-construction [Member]
Nonaccrual And Accruing Troubled Debt Restructured Loans And Lease Modifications [Line Items]
Nonaccrual Loans and Leases	13,531	13,588
Accruing Troubled Debt Restructured Loans and Lease Modifications	2,043	2,397
Total Impaired Loans and Leases	15,574	15,985
Real estate-residential secured for business purpose [Member]
Nonaccrual And Accruing Troubled Debt Restructured Loans And Lease Modifications [Line Items]
Nonaccrual Loans and Leases	169	172
Accruing Troubled Debt Restructured Loans and Lease Modifications
Total Impaired Loans and Leases	169	172
Real estate-residential secured for personal purpose [Member]
Nonaccrual And Accruing Troubled Debt Restructured Loans And Lease Modifications [Line Items]
Nonaccrual Loans and Leases	730	804
Accruing Troubled Debt Restructured Loans and Lease Modifications
Total Impaired Loans and Leases	730	804
Loans to individuals [Member]
Nonaccrual And Accruing Troubled Debt Restructured Loans And Lease Modifications [Line Items]
Nonaccrual Loans and Leases
Accruing Troubled Debt Restructured Loans and Lease Modifications	38	38
Total Impaired Loans and Leases	38	38
Lease financings [Member]
Nonaccrual And Accruing Troubled Debt Restructured Loans And Lease Modifications [Line Items]
Nonaccrual Loans and Leases	343	386
Accruing Troubled Debt Restructured Loans and Lease Modifications	6	19
Total Impaired Loans and Leases	$ 349	$ 405