Loans and Leases - Non-Performing Loans and Leases (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Non-Performing Loans and Leases [Line Items]
Nonaccrual Loans and Leases	$ 17,916	$ 14,183
Accruing Troubled Debt Restructured Loans and Lease Modifications	3,252	5,245
Loans and Leases 90 Days or more Past Due and Accruing Interest	987	379
Total Non- Performing Loans and Leases	22,155	19,807
Nonaccrual Troubled Debt Restructured Loans And Lease Modifications	1,800	93
Commercial, Financial and Agricultural [Member]
Non-Performing Loans and Leases [Line Items]
Nonaccrual Loans and Leases	5,746	6,915
Accruing Troubled Debt Restructured Loans and Lease Modifications	967	1,602
Loans and Leases 90 Days or more Past Due and Accruing Interest	0	0
Total Non- Performing Loans and Leases	6,713	8,517
Real Estate-Commercial [Member]
Non-Performing Loans and Leases [Line Items]
Nonaccrual Loans and Leases	5,651	4,314
Accruing Troubled Debt Restructured Loans and Lease Modifications	1,519	2,449
Loans and Leases 90 Days or more Past Due and Accruing Interest	0	0
Total Non- Performing Loans and Leases	7,170	6,763
Real Estate-Construction [Member]
Non-Performing Loans and Leases [Line Items]
Loans and Leases 90 Days or more Past Due and Accruing Interest	0	0
Real Estate-Residential Secured for Business Purpose [Member]
Non-Performing Loans and Leases [Line Items]
Nonaccrual Loans and Leases	4,898	1,863
Accruing Troubled Debt Restructured Loans and Lease Modifications	766	763
Loans and Leases 90 Days or more Past Due and Accruing Interest	0	0
Total Non- Performing Loans and Leases	5,664	2,626
Real Estate-Residential Secured for Personal Purpose [Member]
Non-Performing Loans and Leases [Line Items]
Nonaccrual Loans and Leases	560	376
Accruing Troubled Debt Restructured Loans and Lease Modifications	0	421
Loans and Leases 90 Days or more Past Due and Accruing Interest	481	0
Total Non- Performing Loans and Leases	1,041	797
Real Estate-Home Equity Secured for Personal Purpose [Member]
Non-Performing Loans and Leases [Line Items]
Nonaccrual Loans and Leases	525	275
Accruing Troubled Debt Restructured Loans and Lease Modifications	0	0
Loans and Leases 90 Days or more Past Due and Accruing Interest	171	0
Total Non- Performing Loans and Leases	696	275
Loans to Individuals [Member]
Non-Performing Loans and Leases [Line Items]
Nonaccrual Loans and Leases	0	0
Accruing Troubled Debt Restructured Loans and Lease Modifications	0	0
Loans and Leases 90 Days or more Past Due and Accruing Interest	142	173
Total Non- Performing Loans and Leases	142	173
Lease Financings [Member]
Non-Performing Loans and Leases [Line Items]
Nonaccrual Loans and Leases	536	440
Accruing Troubled Debt Restructured Loans and Lease Modifications	0	10
Loans and Leases 90 Days or more Past Due and Accruing Interest	193	206
Total Non- Performing Loans and Leases	$ 729	$ 656