Purchased Loans - Loans Acquired with Deteriorated Credit Quality (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Loans acquired with deteriorated credit quality
Total Purchased Credit Deteriorated Loans	$ 9,262,970	$ 9,034,103
Purchased loans | Purchased with deteriorated credit quality
Loans acquired with deteriorated credit quality
Total Purchased Credit Deteriorated Loans	188,114	222,254
Purchased loans | Purchased with deteriorated credit quality | Commercial, financial, agricultural
Loans acquired with deteriorated credit quality
Total Purchased Credit Deteriorated Loans	31,110	29,143
Purchased loans | Purchased with deteriorated credit quality | Real estate – construction
Loans acquired with deteriorated credit quality
Total Purchased Credit Deteriorated Loans	605
Purchased loans | Purchased with deteriorated credit quality | Real estate – 1-4 family mortgage
Loans acquired with deteriorated credit quality
Total Purchased Credit Deteriorated Loans	37,624	48,243
Purchased loans | Purchased with deteriorated credit quality | Real estate – commercial mortgage
Loans acquired with deteriorated credit quality
Total Purchased Credit Deteriorated Loans	115,782	140,438
Purchased loans | Purchased with deteriorated credit quality | Installment loans to individuals
Loans acquired with deteriorated credit quality
Total Purchased Credit Deteriorated Loans	$ 2,993	$ 4,430