FAIR VALUE MEASUREMENTS - Information Regarding the Inputs used in Valuing the Servicer Advances (Details)	3 Months Ended
	Mar. 31, 2022
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value inputs, monthly servicing fee	1070.00%
Servicer Advances | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Outstanding Servicer Advances to UPB of Underlying Residential Mortgage Loans	0.80%
Mortgage Servicing Amount	0.00180
Servicer Advances | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Outstanding Servicer Advances to UPB of Underlying Residential Mortgage Loans	1.80%
Mortgage Servicing Amount	0.00198
Servicer Advances | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Outstanding Servicer Advances to UPB of Underlying Residential Mortgage Loans	1.80%
Mortgage Servicing Amount	0.00198
Prepayment Rate | Servicer Advances | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.051
Prepayment Rate | Servicer Advances | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.066
Prepayment Rate | Servicer Advances | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.065
Delinquency | Servicer Advances | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.082
Delinquency | Servicer Advances | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.150
Delinquency | Servicer Advances | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.148
Discount Rate | Servicer Advances | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.052
Discount Rate | Servicer Advances | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.057
Discount Rate | Servicer Advances | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing asset, measurement input	0.052
Collateral Weighted Average Maturity (Years) | Servicer Advances | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral Weighted Average Maturity (Years)	22 years
Collateral Weighted Average Maturity (Years) | Servicer Advances | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral Weighted Average Maturity (Years)	22 years 1 month 6 days
Collateral Weighted Average Maturity (Years) | Servicer Advances | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral Weighted Average Maturity (Years)	22 years