DERIVATIVE INSTRUMENTS - Effect of Other Derivative Contracts on the Consolidated Statements of Operations and Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Derivative [Line Items]
Unrealized Gain (Loss)	$ (956,272)	$ 1,323,439
Amount of Gain/(Loss) Recognized in Net Gains (Losses) on Derivatives	(184,367)	381,130
Futures
Derivative [Line Items]
Realized Gain (Loss)	118,332	553,154
Unrealized Gain (Loss)	(314,878)	838,952
Amount of Gain/(Loss) Recognized in Net Gains (Losses) on Derivatives	(196,546)	1,392,106
Purchase commitments
Derivative [Line Items]
Realized Gain (Loss)	0	0
Unrealized Gain (Loss)	865	(499)
Amount of Gain/(Loss) Recognized in Net Gains (Losses) on Derivatives	865	(499)
Net TBA derivatives
Derivative [Line Items]
Realized Gain (Loss)	(153,849)	(756,139)
Unrealized Gain (Loss)	215,360	(360,231)
Amount of Gain/(Loss) Recognized in Net Gains (Losses) on Derivatives	61,511	(1,116,370)
Net interest rate swaptions
Derivative [Line Items]
Realized Gain (Loss)	2,323	(14,450)
Unrealized Gain (Loss)	(45,999)	122,622
Amount of Gain/(Loss) Recognized in Net Gains (Losses) on Derivatives	(43,676)	108,172
Credit derivatives
Derivative [Line Items]
Realized Gain (Loss)	(1,312)	1,060
Unrealized Gain (Loss)	(5,209)	(3,339)
Amount of Gain/(Loss) Recognized in Net Gains (Losses) on Derivatives	$ (6,521)	$ (2,279)