DERIVATIVE FINANCIAL INTSTRUMENTS - Summary of Outstanding Swaptions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Assets, at Fair Value	$ 17,160	$ 10,365
Payer Swaption [Member] | Less Than Or Equal To One Year [Member]
Derivatives, Fair Value [Line Items]
Swaption Cost	2,367
Assets, at Fair Value	$ 3,405
Derivative Instruments Average Months To Expiration	8 months
Notional Amount	$ 200,000
Derivative Average Fixed Interest Rate	2.16%
Derivative Avergage Receive Rate	3 Month
Term (Years)	6 years