FAIR VALUE MEASUREMENTS - Inputs used in Valuing the Servicer Advances (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value inputs, monthly servicing fee	0.108%	0.106%
Servicer Advances | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Outstanding Servicer Advances to UPB of Underlying Residential Mortgage Loans	1.20%	0.70%
Servicer Advances | Minimum | Prepayment Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.034	0.065
Servicer Advances | Minimum | Delinquency
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.034	0.082
Servicer Advances | Minimum | Mortgage Servicing Amount or Excess Mortgage Servicing Amount
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.00180	0.00176
Servicer Advances | Minimum | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.057	0.052
Servicer Advances | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Outstanding Servicer Advances to UPB of Underlying Residential Mortgage Loans	2.20%	1.80%
Servicer Advances | Maximum | Prepayment Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.046	0.077
Servicer Advances | Maximum | Delinquency
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.196	0.150
Servicer Advances | Maximum | Mortgage Servicing Amount or Excess Mortgage Servicing Amount
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.00198	0.00198
Servicer Advances | Maximum | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.062	0.057
Servicer Advances | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Outstanding Servicer Advances to UPB of Underlying Residential Mortgage Loans	2.10%	1.70%
Servicer Advances | Weighted Average | Prepayment Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.046	0.077
Servicer Advances | Weighted Average | Delinquency
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.191	0.148
Servicer Advances | Weighted Average | Mortgage Servicing Amount or Excess Mortgage Servicing Amount
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.00198	0.00197
Servicer Advances | Weighted Average | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.057	0.052
Servicer Advances | Weighted Average | Collateral Weighted Average Maturity (Years)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral Weighted Average Maturity (Years)	21 years 10 months 24 days	22 years 1 month 6 days