INVESTMENTS IN REAL ESTATE AND OTHER SECURITIES - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Debt Securities, Available-for-sale [Line Items]
Provision for credit losses on securities	$ (25,134)	$ 8,859	$ 19,015	$ 16,375
Agency RMBS
Debt Securities, Available-for-sale [Line Items]
Face amount of securities purchased	100,000	300,000	100,000	300,000
Purchase of real estate securities, unsettled	100,000	300,000	100,000	300,000
Proceeds from sale of AFS, unsettled		5,300,000		5,300,000
Face amount of securities sold, unsettled	200,000	5,100,000	200,000	5,100,000
Non-Agency
Debt Securities, Available-for-sale [Line Items]
Face amount of securities purchased		21,600		21,600
Purchase of real estate securities, unsettled		$ 13,500		$ 13,500
Proceeds from sale of AFS, unsettled	$ 200,000		$ 200,000