REAL ESTATE AND OTHER SECURITIES - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Agency
Debt Securities, Available-for-sale [Line Items]
Face amount of securities sold	$ 230.0		$ 230.0		$ 490.8
Proceeds of securities sold, unsettled			219.6		471.6
Face amount of securities purchased, unsettled					738.4
Payments for securities purchased, unsettled					$ 730.0
Debt securities, face amount of purchased securities	1,211.3	$ 9,053.2	3,373.7	$ 10,051.4
Treasury
Debt Securities, Available-for-sale [Line Items]
Debt securities, face amount of purchased securities	$ 0.0		$ 1,000.0
Term of treasury bills			6 months