Loans and Leases - Summary of Major Loan and Lease Categories (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	$ 4,951,809	$ 4,386,836	$ 4,167,904
Unearned lease income	16,678	16,340
Net deferred (fees) costs, included in the above table	(5,550)	5,999
Overdraft deposits included in the above table	401	407
Commercial Financial And Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	822,733	947,029	937,149
Paycheck Protection Program Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	498,978	0
Real-Estate Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	2,222,490	2,040,441
Real-Estate Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	212,534	232,595
Real Estate Residential Secured For Business Purpose [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	376,050	373,973	365,640
Real Estate-Residential Secured For Personal Purpose [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	462,512	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	173,041	174,435
Loans to Individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	29,222	29,883	32,485
Lease Financings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases held for investment	$ 154,249	$ 149,421	$ 142,287