Credit Quality of Loans and Allowance for Loan Losses - Schedule of Loans on Nonaccrual Status (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans on nonaccrual status	$ 73,538	$ 49,278
Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans on nonaccrual status	39,218	37,418
Real estate - construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans on nonaccrual status	1,531	66
Real estate – commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans on nonaccrual status	29,916	11,128
Real estate - residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans on nonaccrual status	2,808	618
Installment loans to individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans on nonaccrual status	$ 65	$ 48