Non Purchased Loans (Details 5) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Loan portfolio by risk-rating grades
Total	$ 6,202,709	$ 5,413,462
Commercial, financial, agricultural
Loan portfolio by risk-rating grades
Total	717,490	636,837
Real estate – construction
Loan portfolio by risk-rating grades
Total	552,679	357,665
Real estate – 1-4 family mortgage
Loan portfolio by risk-rating grades
Total	1,878,177	1,735,323
Real estate – commercial mortgage
Loan portfolio by risk-rating grades
Total	2,898,895	2,533,729
Installment loans to individuals
Loan portfolio by risk-rating grades
Total	155,468	149,908
Non-Purchased
Loan portfolio by risk-rating grades
Total	4,713,572	3,830,434
Non-Purchased | Internal Noninvestment Grade
Loan portfolio by risk-rating grades
Total	2,808,367	2,172,918
Non-Purchased | Pass
Loan portfolio by risk-rating grades
Total	2,761,884	2,105,637
Non-Purchased | Watch
Loan portfolio by risk-rating grades
Total	26,416	35,934
Non-Purchased | Substandard
Loan portfolio by risk-rating grades
Total	20,067	31,347
Non-Purchased | Commercial, financial, agricultural | Internal Noninvestment Grade
Loan portfolio by risk-rating grades
Total	439,704	345,419
Non-Purchased | Commercial, financial, agricultural | Pass
Loan portfolio by risk-rating grades
Total	434,323	336,583
Non-Purchased | Commercial, financial, agricultural | Watch
Loan portfolio by risk-rating grades
Total	4,531	8,146
Non-Purchased | Commercial, financial, agricultural | Substandard
Loan portfolio by risk-rating grades
Total	850	690
Non-Purchased | Real estate – construction | Internal Noninvestment Grade
Loan portfolio by risk-rating grades
Total	402,549	224,445
Non-Purchased | Real estate – construction | Pass
Loan portfolio by risk-rating grades
Total	402,156	223,962
Non-Purchased | Real estate – construction | Watch
Loan portfolio by risk-rating grades
Total	393	483
Non-Purchased | Real estate – construction | Substandard
Loan portfolio by risk-rating grades
Total	0	0
Non-Purchased | Real estate – 1-4 family mortgage | Internal Noninvestment Grade
Loan portfolio by risk-rating grades
Total	200,385	155,703
Non-Purchased | Real estate – 1-4 family mortgage | Pass
Loan portfolio by risk-rating grades
Total	190,882	138,852
Non-Purchased | Real estate – 1-4 family mortgage | Watch
Loan portfolio by risk-rating grades
Total	3,374	5,163
Non-Purchased | Real estate – 1-4 family mortgage | Substandard
Loan portfolio by risk-rating grades
Total	6,129	11,688
Non-Purchased | Real estate – commercial mortgage | Internal Noninvestment Grade
Loan portfolio by risk-rating grades
Total	1,765,729	1,447,294
Non-Purchased | Real estate – commercial mortgage | Pass
Loan portfolio by risk-rating grades
Total	1,734,523	1,406,188
Non-Purchased | Real estate – commercial mortgage | Watch
Loan portfolio by risk-rating grades
Total	18,118	22,142
Non-Purchased | Real estate – commercial mortgage | Substandard
Loan portfolio by risk-rating grades
Total	13,088	18,964
Non-Purchased | Installment loans to individuals | Internal Noninvestment Grade
Loan portfolio by risk-rating grades
Total	0	57
Non-Purchased | Installment loans to individuals | Pass
Loan portfolio by risk-rating grades
Total	0	52
Non-Purchased | Installment loans to individuals | Watch
Loan portfolio by risk-rating grades
Total	0	0
Non-Purchased | Installment loans to individuals | Substandard
Loan portfolio by risk-rating grades
Total	$ 0	$ 5