LOANS AND ALLOWANCE FOR LOAN LOSSES (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Period for restructured loan to be considered default	90 days
Provision for unfunded commitments		$ 112
Total loans held for investment, net	$ 9,805,723	6,554,046	$ 7,141,552
Acquired Performing Loan Portfolio
Financing Receivable, Modifications [Line Items]
Total loans held for investment, net	2,900,000		892,400
Remaining discount on acquired loans	44,800		13,700
Purchased Impaired
Financing Receivable, Modifications [Line Items]
Total loans held for investment, net	102,861	$ 57,770	39,021
Purchased impaired loans (gross)	$ 124,500		$ 47,900