LOANS AND ALLOWANCE FOR LOAN LOSSES (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Modifications [Line Items]
Period for restructured loan to be considered default	90 days
Total loans held for investment, net	$ 12,306,997	$ 9,716,207
Acquired Performing Loan Portfolio
Financing Receivable, Modifications [Line Items]
Total loans held for investment, net	3,300,000	2,000,000
Remaining discount on acquired loans	54,100	30,300
Purchased Impaired
Financing Receivable, Modifications [Line Items]
Total loans held for investment, net	89,735	90,221
Purchased impaired loans (gross)	$ 113,800	$ 113,500