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
Purchased
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	2,693,417	2,031,766
Purchased | Performing and Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	619,073	520,075
Purchased | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	614,814	518,604
Purchased | Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	4,259	1,471
Purchased | Commercial, financial, agricultural | Performing and Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	21,372	11,262
Purchased | Commercial, financial, agricultural | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	21,303	11,216
Purchased | Commercial, financial, agricultural | Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	69	46
Purchased | Lease financing | Performing and Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Purchased | Lease financing | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Purchased | Lease financing | Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Purchased | Real estate – construction | Performing and Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	3,185	4,511
Purchased | Real estate – construction | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	3,185	4,511
Purchased | Real estate – construction | Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	0	0
Purchased | Real estate – 1-4 family mortgage | Performing and Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	530,404	460,179
Purchased | Real estate – 1-4 family mortgage | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	526,699	459,038
Purchased | Real estate – 1-4 family mortgage | Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	3,705	1,141
Purchased | Real estate – commercial mortgage | Performing and Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	31,136	27,618
Purchased | Real estate – commercial mortgage | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	30,951	27,495
Purchased | Real estate – commercial mortgage | Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	185	123
Purchased | Installment loans to individuals | Performing and Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	32,976	16,505
Purchased | Installment loans to individuals | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	32,676	16,344
Purchased | Installment loans to individuals | Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 300	$ 161