DERIVATIVE FINANCIAL INTSTRUMENTS - Summary of Outstanding Swaptions (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Net Estimated Fair Value	$ (247)
Notional Amount	375,000
Payer Swaption [Member] | Long [Member]
Derivatives, Fair Value [Line Items]
Swaption Cost	16,860
Net Estimated Fair Value	$ 14,048
Derivative Instruments Average Months To Expiration	14 months
Notional Amount	$ 1,175,000
Derivative Average Fixed Interest Rate	1.26%
Derivative Avergage Receive Rate	3 Month
Term (Years)	9 years
Payer Swaption [Member] | Less Than Or Equal To One Year [Member]
Derivatives, Fair Value [Line Items]
Derivative Avergage Receive Rate		3 Month
Payer Swaption [Member] | Less Than Or Equal To One Year [Member] | Short [Member]
Derivatives, Fair Value [Line Items]
Swaption Cost	$ (4,660)
Net Estimated Fair Value	$ (6,221)
Derivative Instruments Average Months To Expiration	8 months 12 days
Notional Amount	$ 507,700
Derivative Average Fixed Interest Rate	1.49%
Derivative Avergage Receive Rate	3 Month
Term (Years)	12 years 9 months 18 days
Payer Swaption [Member] | Less Than Or Equal To One Year [Member] | Long [Member]
Derivatives, Fair Value [Line Items]
Swaption Cost	$ 3,450
Net Estimated Fair Value	$ 32
Derivative Instruments Average Months To Expiration	5 months 15 days
Notional Amount	$ 500,000
Derivative Average Fixed Interest Rate	0.95%
Derivative Avergage Receive Rate	3 Month
Term (Years)	4 years
Payer Swaption [Member] | One Year To Two Years [Member] | Long [Member]
Derivatives, Fair Value [Line Items]
Swaption Cost	$ 13,410
Net Estimated Fair Value	$ 14,016
Derivative Instruments Average Months To Expiration	20 months 12 days
Notional Amount	$ 675,000
Derivative Average Fixed Interest Rate	1.49%
Derivative Avergage Receive Rate	3 Month
Term (Years)	12 years 9 months 18 days