FAIR VALUE MEASUREMENTS - Information Regarding Inputs used in Valuing Excess MSRs Owned Directly and through Equity Method Investees (Details)	9 Months Ended
	Sep. 30, 2023 $ / Loan
Prepayment Rate | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.001
Prepayment Rate | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.844
Prepayment Rate | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.076
Prepayment Rate | Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.030
Prepayment Rate | Agency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.837
Prepayment Rate | Agency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.064
Prepayment Rate | Non-Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.001
Prepayment Rate | Non-Agency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.844
Prepayment Rate | Non-Agency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.118
Prepayment Rate | Ginnie Mae | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.054
Prepayment Rate | Ginnie Mae | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.815
Prepayment Rate | Ginnie Mae | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.089
Prepayment Rate | Directly Held | Excess MSRs | Minimum
Directly Held
Servicing asset, measurement input	0.023
Prepayment Rate | Directly Held | Excess MSRs | Maximum
Directly Held
Servicing asset, measurement input	0.110
Prepayment Rate | Directly Held | Excess MSRs | Weighted Average
Directly Held
Servicing asset, measurement input	0.059
Prepayment Rate | Held through Equity Method Investees | Excess MSRs | Minimum
Directly Held
Servicing asset, measurement input	0.063
Prepayment Rate | Held through Equity Method Investees | Excess MSRs | Maximum
Directly Held
Servicing asset, measurement input	0.090
Prepayment Rate | Held through Equity Method Investees | Excess MSRs | Weighted Average
Directly Held
Servicing asset, measurement input	0.078
Delinquency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.001
Delinquency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.714
Delinquency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.057
Delinquency | Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.001
Delinquency | Agency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.667
Delinquency | Agency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.021
Delinquency | Non-Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.007
Delinquency | Non-Agency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.700
Delinquency | Non-Agency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.222
Delinquency | Ginnie Mae | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.002
Delinquency | Ginnie Mae | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.714
Delinquency | Ginnie Mae | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.086
Delinquency | Directly Held | Excess MSRs | Minimum
Directly Held
Servicing asset, measurement input	0.002
Delinquency | Directly Held | Excess MSRs | Maximum
Directly Held
Servicing asset, measurement input	0.089
Delinquency | Directly Held | Excess MSRs | Weighted Average
Directly Held
Servicing asset, measurement input	0.044
Delinquency | Held through Equity Method Investees | Excess MSRs | Minimum
Directly Held
Servicing asset, measurement input	0.022
Delinquency | Held through Equity Method Investees | Excess MSRs | Maximum
Directly Held
Servicing asset, measurement input	0.056
Delinquency | Held through Equity Method Investees | Excess MSRs | Weighted Average
Directly Held
Servicing asset, measurement input	0.035
Recapture Rate | Directly Held | Excess MSRs | Minimum
Directly Held
Servicing asset, measurement input	0.000
Recapture Rate | Directly Held | Excess MSRs | Maximum
Directly Held
Servicing asset, measurement input	0.907
Recapture Rate | Directly Held | Excess MSRs | Weighted Average
Directly Held
Servicing asset, measurement input	0.553
Recapture Rate | Held through Equity Method Investees | Excess MSRs | Minimum
Directly Held
Servicing asset, measurement input	0.451
Recapture Rate | Held through Equity Method Investees | Excess MSRs | Maximum
Directly Held
Servicing asset, measurement input	0.643
Recapture Rate | Held through Equity Method Investees | Excess MSRs | Weighted Average
Directly Held
Servicing asset, measurement input	0.590
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.0007
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.0188
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.0033
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.0007
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Agency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.0108
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Agency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.0026
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Non-Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.0010
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Non-Agency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.0188
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Non-Agency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.0046
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Ginnie Mae | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.0018
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Ginnie Mae | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.0116
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Ginnie Mae | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.0043
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Directly Held | Excess MSRs | Minimum
Directly Held
Servicing asset, measurement input	0.0007
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Directly Held | Excess MSRs | Maximum
Directly Held
Servicing asset, measurement input	0.0059
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Directly Held | Excess MSRs | Weighted Average
Directly Held
Servicing asset, measurement input	0.0020
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Held through Equity Method Investees | Excess MSRs | Minimum
Directly Held
Servicing asset, measurement input	0.0016
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Held through Equity Method Investees | Excess MSRs | Maximum
Directly Held
Servicing asset, measurement input	0.0025
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Held through Equity Method Investees | Excess MSRs | Weighted Average
Directly Held
Servicing asset, measurement input	0.0021
Collateral Weighted Average Maturity (Years) | MSRs and MSR Financing Receivables | Minimum
Directly Held
Collateral Weighted Average Maturity (Years)	0 years
Collateral Weighted Average Maturity (Years) | MSRs and MSR Financing Receivables | Maximum
Directly Held
Collateral Weighted Average Maturity (Years)	40 years
Collateral Weighted Average Maturity (Years) | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Collateral Weighted Average Maturity (Years)	24 years
Collateral Weighted Average Maturity (Years) | Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Collateral Weighted Average Maturity (Years)	0 years
Collateral Weighted Average Maturity (Years) | Agency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Collateral Weighted Average Maturity (Years)	40 years
Collateral Weighted Average Maturity (Years) | Agency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Collateral Weighted Average Maturity (Years)	23 years
Collateral Weighted Average Maturity (Years) | Non-Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Collateral Weighted Average Maturity (Years)	0 years
Collateral Weighted Average Maturity (Years) | Non-Agency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Collateral Weighted Average Maturity (Years)	40 years
Collateral Weighted Average Maturity (Years) | Non-Agency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Collateral Weighted Average Maturity (Years)	24 years
Collateral Weighted Average Maturity (Years) | Ginnie Mae | MSRs and MSR Financing Receivables | Minimum
Directly Held
Collateral Weighted Average Maturity (Years)	0 years
Collateral Weighted Average Maturity (Years) | Ginnie Mae | MSRs and MSR Financing Receivables | Maximum
Directly Held
Collateral Weighted Average Maturity (Years)	40 years
Collateral Weighted Average Maturity (Years) | Ginnie Mae | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Collateral Weighted Average Maturity (Years)	27 years
Collateral Weighted Average Maturity (Years) | Directly Held | Excess MSRs | Minimum
Directly Held
Collateral Weighted Average Maturity (Years)	11 years
Collateral Weighted Average Maturity (Years) | Directly Held | Excess MSRs | Maximum
Directly Held
Collateral Weighted Average Maturity (Years)	27 years
Collateral Weighted Average Maturity (Years) | Directly Held | Excess MSRs | Weighted Average
Directly Held
Collateral Weighted Average Maturity (Years)	21 years
Collateral Weighted Average Maturity (Years) | Held through Equity Method Investees | Excess MSRs | Minimum
Directly Held
Collateral Weighted Average Maturity (Years)	15 years
Collateral Weighted Average Maturity (Years) | Held through Equity Method Investees | Excess MSRs | Maximum
Directly Held
Collateral Weighted Average Maturity (Years)	21 years
Collateral Weighted Average Maturity (Years) | Held through Equity Method Investees | Excess MSRs | Weighted Average
Directly Held
Collateral Weighted Average Maturity (Years)	19 years
Measurement Input, Servicing Cost | Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	6.91
Measurement Input, Servicing Cost | Agency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	7.18
Measurement Input, Servicing Cost | Agency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	6.96
Measurement Input, Servicing Cost | Non-Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	7.47
Measurement Input, Servicing Cost | Non-Agency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	9.55
Measurement Input, Servicing Cost | Non-Agency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	9.14
Measurement Input, Servicing Cost | Ginnie Mae | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	8.36