Purchased Loans - Purchased With Deteriorated Credit (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Purchased Credit Deteriorated Loans	$ 9,034,103	$ 7,574,111
Purchased | Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Purchased Credit Deteriorated Loans	222,254	227,260
Purchased | Receivables Acquired with Deteriorated Credit Quality | Commercial, financial, agricultural
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Purchased Credit Deteriorated Loans	29,143	15,315
Purchased | Receivables Acquired with Deteriorated Credit Quality | Lease financing
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Purchased Credit Deteriorated Loans	0	0
Purchased | Receivables Acquired with Deteriorated Credit Quality | Real estate – construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Purchased Credit Deteriorated Loans	0	0
Purchased | Receivables Acquired with Deteriorated Credit Quality | Real estate – 1-4 family mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Purchased Credit Deteriorated Loans	48,243	53,969
Purchased | Receivables Acquired with Deteriorated Credit Quality | Real estate – commercial mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Purchased Credit Deteriorated Loans	140,438	156,338
Purchased | Receivables Acquired with Deteriorated Credit Quality | Installment loans to individuals
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Purchased Credit Deteriorated Loans	$ 4,430	$ 1,638