FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Percentage of instruments with ranges of assumptions used available	99.30%
Real Estate Owned
Schedule of Equity Method Investments [Line Items]
Assets, fair value adjustment	$ (4.3)	$ (2.7)
Properties and Residential Mortgage Loans
Schedule of Equity Method Investments [Line Items]
Assets, fair value adjustment	(38.2)	113.0
Nonrecurring
Schedule of Equity Method Investments [Line Items]
Assets measured at fair value on a nonrecurring basis	130.6	532.1
Nonrecurring | Residential Mortgage Loans Held-for-sale Carried At Lower Cost Or Market
Schedule of Equity Method Investments [Line Items]
Assets measured at fair value on a nonrecurring basis	115.5	504.0
Nonrecurring | Real Estate Owned
Schedule of Equity Method Investments [Line Items]
Assets measured at fair value on a nonrecurring basis	$ 15.1	$ 28.1
Maturity Greater than 30 Days
Schedule of Equity Method Investments [Line Items]
Days delinquent (in days)	30 days
Minimum
Schedule of Equity Method Investments [Line Items]
Recapture rate, term (in months)	3 months
Broker price discount	10.00%
Maximum
Schedule of Equity Method Investments [Line Items]
Recapture rate, term (in months)	6 months
Broker price discount	25.00%
Mortgage Servicing Rights Financing Receivable | LIBOR
Schedule of Equity Method Investments [Line Items]
Variable interest rate spread	2.10%
MSRs | Weighted Average
Schedule of Equity Method Investments [Line Items]
Discount rate	7.40%	8.10%
MSRs | Weighted Average | Excess MSRs Investees
Schedule of Equity Method Investments [Line Items]
Discount rate	7.80%	7.80%
MSRs | Minimum
Schedule of Equity Method Investments [Line Items]
Discount rate	6.90%	7.30%
MSRs | Minimum | Excess MSRs Investees
Schedule of Equity Method Investments [Line Items]
Discount rate	7.50%	7.50%
MSRs | Maximum
Schedule of Equity Method Investments [Line Items]
Discount rate	12.50%	13.00%
MSRs | Maximum | Excess MSRs Investees
Schedule of Equity Method Investments [Line Items]
Discount rate	8.00%	8.00%