FAIR VALUE MEASUREMENTS - Securities Valuation Methodology and Results (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($) source	Dec. 31, 2022 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Outstanding Face Amount	$ 25,589,381
Amortized Cost Basis	8,804,688
Real estate and other securities	$ 8,987,572	$ 8,289,277
Number of broker quotation sources | source	2
Percent of securities	55.50%
Multiple Quotes
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	$ 8,987,558
Single Quote
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	14
Agency
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Outstanding Face Amount	8,041,143
Amortized Cost Basis	7,878,353
Agency | Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	8,041,518
Agency | Level 2 | Multiple Quotes
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	8,041,518
Agency | Level 2 | Single Quote
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	0
Non-Agency
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Outstanding Face Amount	17,548,238
Amortized Cost Basis	926,335
Fair Value	$ 525,004
Non-Agency | Minimum | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non agency RMBS, measurement input	0.050
Non-Agency | Minimum | Prepayment Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non agency RMBS, measurement input	0.000
Non-Agency | Minimum | Delinquency
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non agency RMBS, measurement input	0.000
Non-Agency | Minimum | Loss Severity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non agency RMBS, measurement input	0.000
Non-Agency | Maximum | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non agency RMBS, measurement input	0.150
Non-Agency | Maximum | Prepayment Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non agency RMBS, measurement input	1.000
Non-Agency | Maximum | Delinquency
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non agency RMBS, measurement input	0.200
Non-Agency | Maximum | Loss Severity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non agency RMBS, measurement input	0.740
Non-Agency | Weighted Average | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non agency RMBS, measurement input	0.068
Non-Agency | Weighted Average | Prepayment Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non agency RMBS, measurement input	0.066
Non-Agency | Weighted Average | Delinquency
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non agency RMBS, measurement input	0.002
Non-Agency | Weighted Average | Loss Severity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non agency RMBS, measurement input	0.079
Non-Agency | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	$ 946,054
Non-Agency | Level 3 | Multiple Quotes
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	946,040
Non-Agency | Level 3 | Single Quote
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Real estate and other securities	$ 14