Non Purchased Loans - Performing Status (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 9,083,129	$ 7,620,322
Commercial, financial, agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	1,295,912	1,039,393
Real estate – construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	740,668	633,389
Real estate – 1-4 family mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	2,795,343	2,343,721
Real estate – commercial mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	4,051,509	3,427,530
Installment loans to individuals
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	199,697	176,289
Non-Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	6,389,712	5,588,556
Non-Purchased | Performing and Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	2,560,335	2,210,289
Non-Purchased | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	2,551,833	2,203,941
Non-Purchased | Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	8,502	6,348
Non-Purchased | Commercial, financial, agricultural | Performing and Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	234,547	192,982
Non-Purchased | Commercial, financial, agricultural | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	233,046	191,473
Non-Purchased | Commercial, financial, agricultural | Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	1,501	1,509
Non-Purchased | Lease financing | Performing and Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	61,865	54,013
Non-Purchased | Lease financing | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	61,776	53,854
Non-Purchased | Lease financing | Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	89	159
Non-Purchased | Real estate – construction | Performing and Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	66,551	63,417
Non-Purchased | Real estate – construction | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	66,551	63,417
Non-Purchased | Real estate – construction | Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Non-Purchased | Real estate – 1-4 family mortgage | Performing and Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	1,757,406	1,465,689
Non-Purchased | Real estate – 1-4 family mortgage | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	1,751,994	1,462,347
Non-Purchased | Real estate – 1-4 family mortgage | Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	5,412	3,342
Non-Purchased | Real estate – commercial mortgage | Performing and Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	339,542	331,657
Non-Purchased | Real estate – commercial mortgage | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	338,367	330,441
Non-Purchased | Real estate – commercial mortgage | Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	1,175	1,216
Non-Purchased | Installment loans to individuals | Performing and Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	100,424	102,531
Non-Purchased | Installment loans to individuals | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	100,099	102,409
Non-Purchased | Installment loans to individuals | Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 325	$ 122