LOANS AND ALLOWANCE FOR LOAN LOSSES (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 28,232	$ 26,953	$ 21,700
Nonaccrual interest lost	$ 1,800	2,300	$ 698
Period for restructured loan to be considered default	90 days
Acquired performing loan portfolio	$ 12,610,936	9,716,207
Acquired Performing Loan Portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Acquired performing loan portfolio	3,000,000	2,000,000
Remaining discount on acquired loans	50,100	30,300
Purchased Impaired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Acquired performing loan portfolio	86,681	90,221
Purchased impaired loans (gross)	$ 104,900	$ 113,500