Loans and Leases - Summary of Major Loan and Lease Categories (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	$ 4,448,825	$ 4,386,836	$ 4,067,879
Unearned lease income	16,106	16,340
Net deferred costs, included in the above table	5,754	5,999
Overdraft deposits included in the above table	314	407
Commercial Financial And Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	944,189	947,029	927,638
Real-Estate Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	2,100,699	2,040,441
Real-Estate Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	215,150	232,595
Real Estate Residential Secured For Business Purpose [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	377,644	373,973	360,922
Real Estate-Residential Secured For Personal Purpose [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	454,998	439,059
Real Estate Home Equity Secured For Personal Purpose [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	177,405	174,435
Loans to Individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	29,170	29,883	32,603
Lease Financings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	$ 149,570	$ 149,421	$ 140,509