Purchased Loans (Details 1) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Past due and nonaccrual loans
Total loans, gross	$ 6,238,451	$ 6,205,118
Unearned income	(2,646)	(2,409)
Loans, net of unearned income	6,235,805	6,202,709
Commercial, financial, agricultural
Past due and nonaccrual loans
Total loans, gross	741,466	717,490
Loans, net of unearned income	741,466	717,490
Lease financing
Past due and nonaccrual loans
Total loans, gross	50,462	49,250
Real estate – construction
Past due and nonaccrual loans
Total loans, gross	413,734	552,679
Loans, net of unearned income	413,734	552,679
Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Total loans, gross	1,917,567	1,878,177
Loans, net of unearned income	1,917,567	1,878,177
Real estate – commercial mortgage
Past due and nonaccrual loans
Total loans, gross	3,008,429	2,898,895
Loans, net of unearned income	3,008,429	2,898,895
Installment loans to individuals
Past due and nonaccrual loans
Total loans, gross	106,793	108,627
Loans, net of unearned income	154,609	155,468
Purchased loans
Past due and nonaccrual loans
Total loans, gross	1,401,720	1,489,137
Unearned income	0	0
Loans, net of unearned income	1,401,720	1,489,137
Purchased loans | Accruing Loans
Past due and nonaccrual loans
Current Loans	1,375,100	1,457,912
Unearned income	0	0
Loans, net of unearned income	1,393,225	1,477,790
Purchased loans | Accruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	6,228	9,063
Purchased loans | Accruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	11,897	10,815
Purchased loans | Nonaccruing Loans
Past due and nonaccrual loans
Current Loans	5,146	5,280
Unearned income	0	0
Loans, net of unearned income	8,495	11,347
Purchased loans | Nonaccruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	457	677
Purchased loans | Nonaccruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	2,892	5,390
Purchased loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Total loans, gross	115,229	128,200
Purchased loans | Commercial, financial, agricultural | Accruing Loans
Past due and nonaccrual loans
Current Loans	113,142	125,417
Total loans, gross	114,534	127,230
Purchased loans | Commercial, financial, agricultural | Accruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	524	823
Purchased loans | Commercial, financial, agricultural | Accruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	868	990
Purchased loans | Commercial, financial, agricultural | Nonaccruing Loans
Past due and nonaccrual loans
Current Loans	508	329
Total loans, gross	695	970
Purchased loans | Commercial, financial, agricultural | Nonaccruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	2	260
Purchased loans | Commercial, financial, agricultural | Nonaccruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	185	381
Purchased loans | Lease financing
Past due and nonaccrual loans
Total loans, gross	0	0
Purchased loans | Lease financing | Accruing Loans
Past due and nonaccrual loans
Current Loans	0	0
Total loans, gross	0	0
Purchased loans | Lease financing | Accruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	0	0
Purchased loans | Lease financing | Accruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	0	0
Purchased loans | Lease financing | Nonaccruing Loans
Past due and nonaccrual loans
Current Loans	0	0
Total loans, gross	0	0
Purchased loans | Lease financing | Nonaccruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	0	0
Purchased loans | Lease financing | Nonaccruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	0	0
Purchased loans | Real estate – construction
Past due and nonaccrual loans
Total loans, gross	35,673	68,753
Purchased loans | Real estate – construction | Accruing Loans
Past due and nonaccrual loans
Current Loans	35,514	67,760
Total loans, gross	35,673	68,608
Purchased loans | Real estate – construction | Accruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	159	527
Purchased loans | Real estate – construction | Accruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	0	321
Purchased loans | Real estate – construction | Nonaccruing Loans
Past due and nonaccrual loans
Current Loans	0	0
Total loans, gross	0	145
Purchased loans | Real estate – construction | Nonaccruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	0	0
Purchased loans | Real estate – construction | Nonaccruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	0	145
Purchased loans | Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Total loans, gross	431,904	452,447
Purchased loans | Real estate – 1-4 family mortgage | Accruing Loans
Past due and nonaccrual loans
Current Loans	419,028	440,258
Total loans, gross	427,545	448,212
Purchased loans | Real estate – 1-4 family mortgage | Accruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	4,407	4,572
Purchased loans | Real estate – 1-4 family mortgage | Accruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	4,110	3,382
Purchased loans | Real estate – 1-4 family mortgage | Nonaccruing Loans
Past due and nonaccrual loans
Current Loans	1,626	1,771
Total loans, gross	4,359	4,235
Purchased loans | Real estate – 1-4 family mortgage | Nonaccruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	319	417
Purchased loans | Real estate – 1-4 family mortgage | Nonaccruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	2,414	2,047
Purchased loans | Real estate – commercial mortgage
Past due and nonaccrual loans
Total loans, gross	804,790	823,758
Purchased loans | Real estate – commercial mortgage | Accruing Loans
Past due and nonaccrual loans
Current Loans	793,710	808,886
Total loans, gross	801,520	818,043
Purchased loans | Real estate – commercial mortgage | Accruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	970	3,045
Purchased loans | Real estate – commercial mortgage | Accruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	6,840	6,112
Purchased loans | Real estate – commercial mortgage | Nonaccruing Loans
Past due and nonaccrual loans
Current Loans	2,845	3,054
Total loans, gross	3,270	5,715
Purchased loans | Real estate – commercial mortgage | Nonaccruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	136	0
Purchased loans | Real estate – commercial mortgage | Nonaccruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	289	2,661
Purchased loans | Installment loans to individuals
Past due and nonaccrual loans
Total loans, gross	14,124	15,979
Purchased loans | Installment loans to individuals | Accruing Loans
Past due and nonaccrual loans
Current Loans	13,706	15,591
Total loans, gross	13,953	15,697
Purchased loans | Installment loans to individuals | Accruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	168	96
Purchased loans | Installment loans to individuals | Accruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	79	10
Purchased loans | Installment loans to individuals | Nonaccruing Loans
Past due and nonaccrual loans
Current Loans	167	126
Total loans, gross	171	282
Purchased loans | Installment loans to individuals | Nonaccruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	0	0
Purchased loans | Installment loans to individuals | Nonaccruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	$ 4	$ 156