LOANS - Geographic Concentrations Based on Unpaid Principal Balances (Details) - Residential mortgage loans - Geographic Concentration Risk	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
California
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Geographic Concentrations of Residential Mortgage Loans	48.40%	50.20%
New York
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Geographic Concentrations of Residential Mortgage Loans	11.60%	10.90%
Florida
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Geographic Concentrations of Residential Mortgage Loans	6.80%	6.10%
All other (none individually greater than 5%)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Geographic Concentrations of Residential Mortgage Loans	33.20%	32.80%
All Locations
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Geographic Concentrations of Residential Mortgage Loans	100.00%	100.00%