FAIR VALUE MEASUREMENTS - Securities Valuation Methodology and Results (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($) source	Dec. 31, 2021 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Outstanding Face Amount	$ 25,370,934	$ 24,314,300
Amortized Cost Basis	8,237,819	9,550,336
Real estate and other securities	$ 8,289,277	9,396,539
Number of broker quotation sources | source	2
Percentage of instruments with ranges of assumptions used available	50.40%
Multiple Quotes
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	$ 8,289,263	9,396,539
Single Quote
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	14	0
Agency
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Outstanding Face Amount	7,463,522	8,399,343
Amortized Cost Basis	7,290,473	8,663,693
Agency | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	7,338,417	8,444,597
Agency | Multiple Quotes | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	7,338,417	8,444,597
Agency | Single Quote | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	0	0
Non-Agency
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Outstanding Face Amount	17,907,412	15,914,957
Amortized Cost Basis	947,346	886,643
Fair Value	$ 479,406
Non-Agency | Discount Rate | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Agency RMBS, measurement input	0.035
Non-Agency | Discount Rate | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Agency RMBS, measurement input	0.150
Non-Agency | Discount Rate | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Agency RMBS, measurement input	0.065
Non-Agency | Prepayment Rate | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Agency RMBS, measurement input	0.000
Non-Agency | Prepayment Rate | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Agency RMBS, measurement input	0.250
Non-Agency | Prepayment Rate | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Agency RMBS, measurement input	0.111
Non-Agency | CDR | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Agency RMBS, measurement input	0.000
Non-Agency | CDR | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Agency RMBS, measurement input	0.120
Non-Agency | CDR | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Agency RMBS, measurement input	0.006
Non-Agency | Loss Severity | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Agency RMBS, measurement input	0.000
Non-Agency | Loss Severity | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Agency RMBS, measurement input	0.880
Non-Agency | Loss Severity | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Agency RMBS, measurement input	0.103
Non-Agency | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	$ 950,860	951,942
Non-Agency | Multiple Quotes | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	950,846	951,942
Non-Agency | Single Quote | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	$ 14	$ 0