REAL ESTATE AND OTHER SECURITIES - Narrative (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Proceeds from sale of available-for-sale securities, unsettled		$ 0
RMBS Designated as AFS
Debt Securities, Available-for-sale [Line Items]
Face amount of securities sold, unsettled	$ 1,100,000,000
Proceeds from sale of available-for-sale securities, unsettled	$ 1,100,000,000