LOANS AND ALLOWANCE FOR LOAN LOSSES (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Period for restructured loan to be considered default	90 days
Provision for loan losses	$ (9,103)	$ (7,360)
Total loans held for investment, net	9,411,598		$ 7,141,552
Acquired Performing Loan Portfolio
Financing Receivable, Modifications [Line Items]
Total loans held for investment, net	2,200,000		892,400
Remaining discount on acquired loans	33,400		13,700
Purchased Impaired
Financing Receivable, Modifications [Line Items]
Total loans held for investment, net	94,746		39,021
Purchased impaired loans (gross)	$ 119,100		$ 47,900