Purchased Loans - Loans Acquired with Deteriorated Credit Quality (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Loans acquired with deteriorated credit quality
Total Purchased Credit Deteriorated Loans	$ 7,651,669	$ 7,574,111
Purchased loans | Receivables Acquired with Deteriorated Credit Quality
Loans acquired with deteriorated credit quality
Total Purchased Credit Deteriorated Loans	214,310	227,260
Purchased loans | Receivables Acquired with Deteriorated Credit Quality | Commercial, financial, agricultural
Loans acquired with deteriorated credit quality
Total Purchased Credit Deteriorated Loans	12,933	15,315
Purchased loans | Receivables Acquired with Deteriorated Credit Quality | Real estate – 1-4 family mortgage
Loans acquired with deteriorated credit quality
Total Purchased Credit Deteriorated Loans	50,196	53,969
Purchased loans | Receivables Acquired with Deteriorated Credit Quality | Real estate – commercial mortgage
Loans acquired with deteriorated credit quality
Total Purchased Credit Deteriorated Loans	149,547	156,338
Purchased loans | Receivables Acquired with Deteriorated Credit Quality | Installment loans to individuals
Loans acquired with deteriorated credit quality
Total Purchased Credit Deteriorated Loans	$ 1,634	$ 1,638