SECURITIZATIONS AND VARIABLE INTEREST ENTITIES - Loan Delinquencies and Liquidation Losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Residential mortgages
Variable Interest Entity
Securitized assets	$ 28,100.0		$ 28,100.0		$ 30,800.0
Liquidation losses	(0.2)	$ 1.0	4.4	$ 3.0
Commercial and other
Variable Interest Entity
Securitized assets	29,200.0		29,200.0		28,800.0
Liquidation losses	0.0	0.0	0.0	0.0
Mortgage securitizations - Non-agency-sponsored
Variable Interest Entity
Securitized assets	57,300.0		57,300.0		59,600.0
Liquidation losses	(0.2)	$ 1.0	4.4	$ 3.0
Personal loan
Variable Interest Entity
Securitized assets	100.0		100.0
90+ days past due | Residential mortgages
Variable Interest Entity
Securitized assets	400.0		400.0		500.0
90+ days past due | Commercial and other
Variable Interest Entity
Securitized assets	0.0		0.0		0.0
90+ days past due | Mortgage securitizations - Non-agency-sponsored
Variable Interest Entity
Securitized assets	$ 400.0		$ 400.0		$ 500.0