REAL ESTATE AND OTHER SECURITIES - Schedule of Real Estate and Other Securities by Designation (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($) security	Dec. 31, 2023 USD ($)
Debt Securities, Available-for-sale [Line Items]
Carrying Value	$ 15,289,314	$ 9,757,664
Weighted Average Life (Years)	1 year 2 months 12 days
Investments	$ 32,648,150
Residual Bonds
Debt Securities, Available-for-sale [Line Items]
Investments	30,100
AFS Agency
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	73,387
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Carrying Value	$ 64,331	65,496
Number of Securities | security	1
Weighted Average Coupon	3.50%
Weighted Average Yield	3.50%
Weighted Average Life (Years)	10 years 9 months 18 days
AFS Non-Agency
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	$ 2,439,560
Gross Unrealized Gains	70,861
Gross Unrealized Losses	(25,123)
Carrying Value	$ 356,232	363,157
Number of Securities | security	330
Weighted Average Coupon	3.60%
Weighted Average Yield	4.00%
Weighted Average Life (Years)	5 years 7 months 6 days
FVO Agency
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	$ 9,678,119
Gross Unrealized Gains	41,444
Gross Unrealized Losses	(24,684)
Carrying Value	$ 9,501,879	8,467,634
Number of Securities | security	46
Weighted Average Coupon	5.10%
Weighted Average Yield	5.10%
Weighted Average Life (Years)	11 years
Treasury
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	$ 4,500,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(8,759)
Carrying Value	$ 4,472,656	0
Number of Securities | security	7
Weighted Average Coupon	4.30%
Weighted Average Yield	4.30%
Weighted Average Life (Years)	4 years 1 month 6 days
FVO Non-Agency
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	$ 17,022,510
Gross Unrealized Gains	71,080
Gross Unrealized Losses	(83,634)
Carrying Value	$ 894,216	861,377
Number of Securities | security	570
Weighted Average Coupon	4.10%
Weighted Average Yield	7.30%
Weighted Average Life (Years)	7 years 8 months 12 days
Agency and Non-Agency Residential Mortgage Backed Securities
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	$ 33,713,576
Gross Unrealized Gains	183,385
Gross Unrealized Losses	(142,200)
Carrying Value	$ 15,289,314	$ 9,757,664
Number of Securities | security	954
Weighted Average Coupon	4.80%
Weighted Average Yield	5.00%
Weighted Average Life (Years)	8 years 8 months 12 days
Agency
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	$ 9,751,506
Agency | Fixed Rate Securities
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	14,300,000
Non-Agency
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	19,462,070
Non-Agency | Fixed Rate Securities
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	7,700,000
Residual and interest - only notional amount	6,700,000
Non-Agency | Floating Rate Securities
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	11,800,000
Residual and interest - only notional amount	11,300,000
Consumer loan bonds
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	280
Gross Unrealized Gains	259
Gross Unrealized Losses	0
Carrying Value	$ 259
Number of Securities | security	1
Weighted Average Life (Years)	1 year 6 months
Interest-only securities
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	$ 11,490,623
Gross Unrealized Gains	38,577
Gross Unrealized Losses	(29,862)
Carrying Value	$ 149,463
Number of Securities | security	151
Weighted Average Coupon	1.00%
Weighted Average Yield	11.40%
Weighted Average Life (Years)	2 years 3 months 18 days
Servicing strips
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	$ 3,930,230
Gross Unrealized Gains	14,107
Gross Unrealized Losses	(2,714)
Carrying Value	$ 41,779
Number of Securities | security	61
Weighted Average Coupon	0.30%
Weighted Average Yield	13.10%
Weighted Average Life (Years)	3 years 8 months 12 days
Commercial MBSs
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	$ 3,845
Gross Unrealized Gains	194
Gross Unrealized Losses	0
Carrying Value	$ 3,901
Number of Securities | security	2
Weighted Average Coupon	7.90%
Weighted Average Yield	7.90%
Weighted Average Life (Years)	1 year 2 months 12 days
CLOs
Debt Securities, Available-for-sale [Line Items]
Outstanding Face Amount	$ 215,412
Gross Unrealized Gains	4,425
Gross Unrealized Losses	(2,403)
Carrying Value	$ 211,996
Number of Securities | security	194
Weighted Average Coupon	5.50%
Weighted Average Yield	8.70%
Weighted Average Life (Years)	8 years 7 months 6 days