DERIVATIVE FINANCIAL INSTRUMENTS - Effect on the consolidated statements of operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
(Losses) gains on derivative instruments	$ 26,877	$ (79,092)	$ (51,176)
Eurodollar Future [Member] | Short [Member]
Derivatives, Fair Value [Line Items]
(Losses) gains on derivative instruments	(10)	(8,337)	(13,860)
Treasury Note Future [Member] | Short [Member]
Derivatives, Fair Value [Line Items]
(Losses) gains on derivative instruments	(846)	(4,707)	(5,175)
Fed Funds Future [Member] | Short [Member]
Derivatives, Fair Value [Line Items]
(Losses) gains on derivative instruments	0	0	177
Swap [Member]
Derivatives, Fair Value [Line Items]
(Losses) gains on derivative instruments	23,613	(66,212)	(26,582)
Payer Swaption [Member] | Short [Member]
Derivatives, Fair Value [Line Items]
(Losses) gains on derivative instruments	9,062	(3,070)	0
Payer Swaption [Member] | Long [Member]
Derivatives, Fair Value [Line Items]
(Losses) gains on derivative instruments	(2,580)	98	(1,379)
Interest Rate Floor [Member]
Derivatives, Fair Value [Line Items]
(Losses) gains on derivative instruments	2,765	0	0
TBA Contracts [Member] | Short [Member]
Derivatives, Fair Value [Line Items]
(Losses) gains on derivative instruments	3,432	(6,719)	(6,264)
TBA Contracts [Member] | Long [Member]
Derivatives, Fair Value [Line Items]
(Losses) gains on derivative instruments	(8,559)	9,950	1,907
US Treasury Securities [Member] | Short [Member]
Derivatives, Fair Value [Line Items]
(Losses) gains on derivative instruments	$ 0	$ (95)	$ 0