Purchased Loans (Details 1) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Past due and nonaccrual loans
Total loans, gross	$ 6,374,288	$ 6,205,118
Unearned income	(3,281)	(2,409)
Loans, net of unearned income	6,371,007	6,202,709
Commercial, financial, agricultural
Past due and nonaccrual loans
Total loans, gross	760,582	717,490
Loans, net of unearned income	760,582	717,490
Real estate – construction
Past due and nonaccrual loans
Total loans, gross	460,807	552,679
Loans, net of unearned income	460,807	552,679
Real estate – 1-4 family mortgage
Past due and nonaccrual loans
Total loans, gross	1,952,394	1,878,177
Loans, net of unearned income	1,952,394	1,878,177
Real estate – commercial mortgage
Past due and nonaccrual loans
Total loans, gross	3,040,963	2,898,895
Loans, net of unearned income	3,040,963	2,898,895
Installment loans to individuals
Past due and nonaccrual loans
Total loans, gross	107,195	108,627
Loans, net of unearned income	156,261	155,468
Purchased loans
Past due and nonaccrual loans
Total loans, gross	1,312,109	1,489,137
Unearned income	0	0
Loans, net of unearned income	1,312,109	1,489,137
Purchased loans | Accruing Loans
Past due and nonaccrual loans
Current Loans	1,293,575	1,457,912
Unearned income	0	0
Loans, net of unearned income	1,306,182	1,477,790
Purchased loans | Accruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	4,479	9,063
Purchased loans | Accruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	8,128	10,815
Purchased loans | Nonaccruing Loans
Past due and nonaccrual loans
Current Loans	3,040	5,280
Unearned income	0	0
Loans, net of unearned income	5,927	11,347
Purchased loans | Nonaccruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	217	677
Purchased loans | Nonaccruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	2,670	5,390
Purchased loans | Commercial, financial, agricultural
Past due and nonaccrual loans
Total loans, gross	102,869	128,200
Purchased loans | Commercial, financial, agricultural | Accruing Loans
Past due and nonaccrual loans
Current Loans	101,732	125,417
Total loans, gross	102,420	127,230
Purchased loans | Commercial, financial, agricultural | Accruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	124	823
Purchased loans | Commercial, financial, agricultural | Accruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	564	990
Purchased loans | Commercial, financial, agricultural | Nonaccruing Loans
Past due and nonaccrual loans
Current Loans	276	329
Total loans, gross	449	970
Purchased loans | Commercial, financial, agricultural | Nonaccruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	0	260
Purchased loans | Commercial, financial, agricultural | Nonaccruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	173	381
Purchased loans | Real estate – construction
Past due and nonaccrual loans
Total loans, gross	35,946	68,753
Purchased loans | Real estate – construction | Accruing Loans
Past due and nonaccrual loans
Current Loans	35,946	67,760
Total loans, gross	35,946	68,608
Purchased loans | Real estate – construction | Accruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	0	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	400,460	452,447
Purchased loans | Real estate – 1-4 family mortgage | Accruing Loans
Past due and nonaccrual loans
Current Loans	391,218	440,258
Total loans, gross	396,791	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	2,363	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	3,210	3,382
Purchased loans | Real estate – 1-4 family mortgage | Nonaccruing Loans
Past due and nonaccrual loans
Current Loans	1,254	1,771
Total loans, gross	3,669	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	207	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	2,208	2,047
Purchased loans | Real estate – commercial mortgage
Past due and nonaccrual loans
Total loans, gross	759,743	823,758
Purchased loans | Real estate – commercial mortgage | Accruing Loans
Past due and nonaccrual loans
Current Loans	751,880	808,886
Total loans, gross	758,101	818,043
Purchased loans | Real estate – commercial mortgage | Accruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	1,874	3,045
Purchased loans | Real estate – commercial mortgage | Accruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	4,347	6,112
Purchased loans | Real estate – commercial mortgage | Nonaccruing Loans
Past due and nonaccrual loans
Current Loans	1,355	3,054
Total loans, gross	1,642	5,715
Purchased loans | Real estate – commercial mortgage | Nonaccruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	0	0
Purchased loans | Real estate – commercial mortgage | Nonaccruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	287	2,661
Purchased loans | Installment loans to individuals
Past due and nonaccrual loans
Total loans, gross	13,091	15,979
Purchased loans | Installment loans to individuals | Accruing Loans
Past due and nonaccrual loans
Current Loans	12,799	15,591
Total loans, gross	12,924	15,697
Purchased loans | Installment loans to individuals | Accruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	118	96
Purchased loans | Installment loans to individuals | Accruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	7	10
Purchased loans | Installment loans to individuals | Nonaccruing Loans
Past due and nonaccrual loans
Current Loans	155	126
Total loans, gross	167	282
Purchased loans | Installment loans to individuals | Nonaccruing Loans | 30-89 Days Past Due
Past due and nonaccrual loans
Loans past due	10	0
Purchased loans | Installment loans to individuals | Nonaccruing Loans | 90 Days or More Past Due
Past due and nonaccrual loans
Loans past due	$ 2	$ 156