Non Purchased Loans - Loan Portfolio Not Subject to Risk Rating (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Loan portfolio not subject to risk rating
Total	$ 9,313,784	$ 9,083,129
Commercial, financial, agricultural
Loan portfolio not subject to risk rating
Total	1,328,560	1,295,912
Real estate – construction
Loan portfolio not subject to risk rating
Total	816,695	740,668
Real estate – 1-4 family mortgage
Loan portfolio not subject to risk rating
Total	2,797,633	2,795,343
Real estate – commercial mortgage
Loan portfolio not subject to risk rating
Total	4,022,375	4,051,509
Installment loans to individuals
Loan portfolio not subject to risk rating
Total	348,521	199,697
Non purchased loans and leases
Loan portfolio not subject to risk rating
Total	7,031,818	6,389,712
Non purchased loans and leases | Performing and Nonperforming
Loan portfolio not subject to risk rating
Total	2,754,635	2,560,335
Non purchased loans and leases | Performing and Nonperforming | Commercial, financial, agricultural
Loan portfolio not subject to risk rating
Total	221,275	234,547
Non purchased loans and leases | Performing and Nonperforming | Lease financing
Loan portfolio not subject to risk rating
Total	69,953	61,865
Non purchased loans and leases | Performing and Nonperforming | Real estate – construction
Loan portfolio not subject to risk rating
Total	61,640	66,551
Non purchased loans and leases | Performing and Nonperforming | Real estate – 1-4 family mortgage
Loan portfolio not subject to risk rating
Total	1,908,504	1,757,406
Non purchased loans and leases | Performing and Nonperforming | Real estate – commercial mortgage
Loan portfolio not subject to risk rating
Total	330,260	339,542
Non purchased loans and leases | Performing and Nonperforming | Installment loans to individuals
Loan portfolio not subject to risk rating
Total	163,003	100,424
Non purchased loans and leases | Performing
Loan portfolio not subject to risk rating
Total	2,741,291	2,551,833
Non purchased loans and leases | Performing | Commercial, financial, agricultural
Loan portfolio not subject to risk rating
Total	219,469	233,046
Non purchased loans and leases | Performing | Lease financing
Loan portfolio not subject to risk rating
Total	69,549	61,776
Non purchased loans and leases | Performing | Real estate – construction
Loan portfolio not subject to risk rating
Total	61,258	66,551
Non purchased loans and leases | Performing | Real estate – 1-4 family mortgage
Loan portfolio not subject to risk rating
Total	1,899,433	1,751,994
Non purchased loans and leases | Performing | Real estate – commercial mortgage
Loan portfolio not subject to risk rating
Total	328,755	338,367
Non purchased loans and leases | Performing | Installment loans to individuals
Loan portfolio not subject to risk rating
Total	162,827	100,099
Non purchased loans and leases | Non- Performing
Loan portfolio not subject to risk rating
Total	13,344	8,502
Non purchased loans and leases | Non- Performing | Commercial, financial, agricultural
Loan portfolio not subject to risk rating
Total	1,806	1,501
Non purchased loans and leases | Non- Performing | Lease financing
Loan portfolio not subject to risk rating
Total	404	89
Non purchased loans and leases | Non- Performing | Real estate – construction
Loan portfolio not subject to risk rating
Total	382	0
Non purchased loans and leases | Non- Performing | Real estate – 1-4 family mortgage
Loan portfolio not subject to risk rating
Total	9,071	5,412
Non purchased loans and leases | Non- Performing | Real estate – commercial mortgage
Loan portfolio not subject to risk rating
Total	1,505	1,175
Non purchased loans and leases | Non- Performing | Installment loans to individuals
Loan portfolio not subject to risk rating
Total	$ 176	$ 325