Purchased Loans (Details 6) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Loan portfolio not subject to risk rating
Total	$ 6,235,805	$ 6,202,709
Commercial, financial, agricultural
Loan portfolio not subject to risk rating
Total	741,466	717,490
Real estate – construction
Loan portfolio not subject to risk rating
Total	413,734	552,679
Real estate – 1-4 family mortgage
Loan portfolio not subject to risk rating
Total	1,917,567	1,878,177
Real estate – commercial mortgage
Loan portfolio not subject to risk rating
Total	3,008,429	2,898,895
Installment loans to individuals
Loan portfolio not subject to risk rating
Total	154,609	155,468
Purchased loans
Loan portfolio not subject to risk rating
Total	1,401,720	1,489,137
Purchased loans | Performing and Nonperforming
Loan portfolio not subject to risk rating
Total	299,420	316,127
Purchased loans | Performing
Loan portfolio not subject to risk rating
Total	297,350	313,852
Purchased loans | Non-Performing
Loan portfolio not subject to risk rating
Total	2,070	2,275
Purchased loans | Commercial, financial, agricultural | Performing and Nonperforming
Loan portfolio not subject to risk rating
Total	9,297	9,568
Purchased loans | Commercial, financial, agricultural | Performing
Loan portfolio not subject to risk rating
Total	9,234	9,489
Purchased loans | Commercial, financial, agricultural | Non-Performing
Loan portfolio not subject to risk rating
Total	63	79
Purchased loans | Lease financing | Performing and Nonperforming
Loan portfolio not subject to risk rating
Total	0	0
Purchased loans | Lease financing | Performing
Loan portfolio not subject to risk rating
Total	0	0
Purchased loans | Lease financing | Non-Performing
Loan portfolio not subject to risk rating
Total	0	0
Purchased loans | Real estate – construction | Performing and Nonperforming
Loan portfolio not subject to risk rating
Total	1,268	4,067
Purchased loans | Real estate – construction | Performing
Loan portfolio not subject to risk rating
Total	1,268	3,601
Purchased loans | Real estate – construction | Non-Performing
Loan portfolio not subject to risk rating
Total	0	466
Purchased loans | Real estate – 1-4 family mortgage | Performing and Nonperforming
Loan portfolio not subject to risk rating
Total	254,890	267,201
Purchased loans | Real estate – 1-4 family mortgage | Performing
Loan portfolio not subject to risk rating
Total	253,172	265,697
Purchased loans | Real estate – 1-4 family mortgage | Non-Performing
Loan portfolio not subject to risk rating
Total	1,718	1,504
Purchased loans | Real estate – commercial mortgage | Performing and Nonperforming
Loan portfolio not subject to risk rating
Total	21,772	21,411
Purchased loans | Real estate – commercial mortgage | Performing
Loan portfolio not subject to risk rating
Total	21,715	21,353
Purchased loans | Real estate – commercial mortgage | Non-Performing
Loan portfolio not subject to risk rating
Total	57	58
Purchased loans | Installment loans to individuals | Performing and Nonperforming
Loan portfolio not subject to risk rating
Total	12,193	13,880
Purchased loans | Installment loans to individuals | Performing
Loan portfolio not subject to risk rating
Total	11,961	13,712
Purchased loans | Installment loans to individuals | Non-Performing
Loan portfolio not subject to risk rating
Total	$ 232	$ 168