DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Derivative Assets and Liabilties (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Assets, at Fair Value	$ 95,752,000	$ 20,999,000
Liabilities, at Fair Value	35,057,000	33,227,000
Restricted cash	117,155,000	79,363,000
Other Liabilities	22,306,000	7,188,000
Not Designated as Hedging Instrument, Economic Hedge [Member]
Derivative [Line Items]
Assets, at Fair Value	95,752,000	20,999,000
Liabilities, at Fair Value	35,057,000	33,227,000
Interest Rate Swap [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member]
Derivative [Line Items]
Assets, at Fair Value	25,254,000	7,000
Liabilities, at Fair Value	0	24,711,000
Restricted cash	12,214,000	19,761,000
TBA Contracts [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member]
Derivative [Line Items]
Assets, at Fair Value	9,456,000	3,559,000
Liabilities, at Fair Value	0	786,000
Restricted cash	1,781,000	284,000
Other Liabilities	7,407,000	2,520,000
Eurodollar Future Margin [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member]
Derivative [Line Items]
Restricted cash	585,000	489,000
Payer Swaption [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member]
Derivative [Line Items]
Other Liabilities	13,962,000	3,563,000
Payer Swaption [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member] | Short [Member]
Derivative [Line Items]
Liabilities, at Fair Value	35,057,000	7,730,000
Payer Swaption [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member] | Long [Member]
Derivative [Line Items]
Assets, at Fair Value	58,643,000	17,433,000
Interest Rate Floor [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member]
Derivative [Line Items]
Assets, at Fair Value	$ 2,399,000	$ 0