Non Purchased Loans - Loan Portfolio Not Subject to Risk Rating (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Loan portfolio not subject to risk rating
Total	$ 7,448,608	$ 6,202,709
Commercial, financial, agricultural
Loan portfolio not subject to risk rating
Total	1,008,935	717,490
Real estate – construction
Loan portfolio not subject to risk rating
Total	577,720	552,679
Real estate – 1-4 family mortgage
Loan portfolio not subject to risk rating
Total	2,295,852	1,878,177
Real estate – commercial mortgage
Loan portfolio not subject to risk rating
Total	3,390,389	2,898,895
Installment loans to individuals
Loan portfolio not subject to risk rating
Total	175,712	155,468
Non purchased loans and leases
Loan portfolio not subject to risk rating
Total	5,293,467	4,713,572
Non purchased loans and leases | Performing and Nonperforming
Loan portfolio not subject to risk rating
Total	2,104,649	1,905,205
Non purchased loans and leases | Performing and Nonperforming | Commercial, financial, agricultural
Loan portfolio not subject to risk rating
Total	180,194	149,586
Non purchased loans and leases | Performing and Nonperforming | Lease financing
Loan portfolio not subject to risk rating
Total	51,902	46,841
Non purchased loans and leases | Performing and Nonperforming | Real estate – construction
Loan portfolio not subject to risk rating
Total	62,252	81,377
Non purchased loans and leases | Performing and Nonperforming | Real estate – 1-4 family mortgage
Loan portfolio not subject to risk rating
Total	1,387,206	1,225,345
Non purchased loans and leases | Performing and Nonperforming | Real estate – commercial mortgage
Loan portfolio not subject to risk rating
Total	322,907	309,408
Non purchased loans and leases | Performing and Nonperforming | Installment loans to individuals
Loan portfolio not subject to risk rating
Total	100,188	92,648
Non purchased loans and leases | Performing
Loan portfolio not subject to risk rating
Total	2,098,640	1,900,508
Non purchased loans and leases | Performing | Commercial, financial, agricultural
Loan portfolio not subject to risk rating
Total	178,294	148,499
Non purchased loans and leases | Performing | Lease financing
Loan portfolio not subject to risk rating
Total	51,737	46,703
Non purchased loans and leases | Performing | Real estate – construction
Loan portfolio not subject to risk rating
Total	62,252	81,377
Non purchased loans and leases | Performing | Real estate – 1-4 family mortgage
Loan portfolio not subject to risk rating
Total	1,384,865	1,222,816
Non purchased loans and leases | Performing | Real estate – commercial mortgage
Loan portfolio not subject to risk rating
Total	321,404	308,609
Non purchased loans and leases | Performing | Installment loans to individuals
Loan portfolio not subject to risk rating
Total	100,088	92,504
Non purchased loans and leases | Non- Performing
Loan portfolio not subject to risk rating
Total	6,009	4,697
Non purchased loans and leases | Non- Performing | Commercial, financial, agricultural
Loan portfolio not subject to risk rating
Total	1,900	1,087
Non purchased loans and leases | Non- Performing | Lease financing
Loan portfolio not subject to risk rating
Total	165	138
Non purchased loans and leases | Non- Performing | Real estate – construction
Loan portfolio not subject to risk rating
Total	0	0
Non purchased loans and leases | Non- Performing | Real estate – 1-4 family mortgage
Loan portfolio not subject to risk rating
Total	2,341	2,529
Non purchased loans and leases | Non- Performing | Real estate – commercial mortgage
Loan portfolio not subject to risk rating
Total	1,503	799
Non purchased loans and leases | Non- Performing | Installment loans to individuals
Loan portfolio not subject to risk rating
Total	$ 100	$ 144