LOANS - Additional Data On Residential Mortgage Loans (Details) - Residential Mortgage Loans $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024 USD ($) point	Dec. 31, 2023 USD ($) point
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Unpaid principal balance	$ 19,364,991	$ 16,611,204
Minimum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Unpaid principal balance	$ 1	$ 1
Interest rate	2.00%	2.00%
FICO score at loan origination | point	549	549
Loan-to-value ratio at loan origination	3.00%	3.00%
Maximum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Unpaid principal balance	$ 4,396	$ 4,396
Interest rate	13.25%	13.25%
FICO score at loan origination | point	850	850
Loan-to-value ratio at loan origination	100.00%	100.00%
Weighted Average
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Unpaid principal balance	$ 475	$ 477
Interest rate	5.87%	5.63%
FICO score at loan origination | point	757	758
Loan-to-value ratio at loan origination	69.00%	68.00%