Loans and Leases - Non-Performing Loans and Leases (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Non-Performing Loans and Leases [Line Items]
Nonaccrual loans and leases	$ 31,692	$ 38,578
Accruing troubled debt restructured loans and lease modifications	53	54
Loans and leases 90 days or more past due and accruing interest	1,392	143
Total Nonperforming Loans and Leases	33,137	38,775
Nonaccrual troubled debt restructured loans and lease modifications	14,100	13,800
Commercial, Financial and Agricultural [Member]
Non-Performing Loans and Leases [Line Items]
Nonaccrual loans and leases	2,827	3,442
Accruing troubled debt restructured loans and lease modifications	0	0
Loans and leases 90 days or more past due and accruing interest	50	20
Total Nonperforming Loans and Leases	2,877	3,462
Real Estate-Commercial [Member]
Non-Performing Loans and Leases [Line Items]
Nonaccrual loans and leases	22,739	27,928
Accruing troubled debt restructured loans and lease modifications	0	0
Loans and leases 90 days or more past due and accruing interest	945	0
Total Nonperforming Loans and Leases	23,684	27,928
Real Estate-Construction [Member]
Non-Performing Loans and Leases [Line Items]
Nonaccrual loans and leases	0	257
Accruing troubled debt restructured loans and lease modifications	0	0
Loans and leases 90 days or more past due and accruing interest	0	0
Total Nonperforming Loans and Leases	0	257
Real Estate-Residential Secured for Business Purpose [Member]
Non-Performing Loans and Leases [Line Items]
Nonaccrual loans and leases	2,786	2,980
Accruing troubled debt restructured loans and lease modifications	0	0
Loans and leases 90 days or more past due and accruing interest	0	0
Total Nonperforming Loans and Leases	2,786	2,980
Real Estate-Residential Secured for Personal Purpose [Member]
Non-Performing Loans and Leases [Line Items]
Nonaccrual loans and leases	2,086	2,038
Accruing troubled debt restructured loans and lease modifications	0	0
Loans and leases 90 days or more past due and accruing interest	0	0
Total Nonperforming Loans and Leases	2,086	2,038
Real Estate-Home Equity Secured for Personal Purpose [Member]
Non-Performing Loans and Leases [Line Items]
Nonaccrual loans and leases	1,047	1,427
Accruing troubled debt restructured loans and lease modifications	53	54
Loans and leases 90 days or more past due and accruing interest	0	0
Total Nonperforming Loans and Leases	1,100	1,481
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	185	74
Total Nonperforming Loans and Leases	185	74
Lease Financings [Member]
Non-Performing Loans and Leases [Line Items]
Nonaccrual loans and leases	207	506
Accruing troubled debt restructured loans and lease modifications	0	0
Loans and leases 90 days or more past due and accruing interest	212	49
Total Nonperforming Loans and Leases	$ 419	$ 555