FAIR VALUE MEASUREMENTS - Information Regarding Inputs used in Valuing Excess MSRs Owned Directly and through Equity Method Investees (Details)	6 Months Ended
	Jun. 30, 2023 $ / Loan
Prepayment Rate | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.003
Prepayment Rate | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.995
Prepayment Rate | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.106
Prepayment Rate | Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.003
Prepayment Rate | Agency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.995
Prepayment Rate | Agency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.104
Prepayment Rate | Non-Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.005
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	0.130
Prepayment Rate | Ginnie Mae | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.004
Prepayment Rate | Ginnie Mae | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.825
Prepayment Rate | Ginnie Mae | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.103
Prepayment Rate | Directly Held | Excess MSRs | Minimum
Directly Held
Servicing asset, measurement input	0.029
Prepayment Rate | Directly Held | Excess MSRs | Maximum
Directly Held
Servicing asset, measurement input	0.122
Prepayment Rate | Directly Held | Excess MSRs | Weighted Average
Directly Held
Servicing asset, measurement input	0.066
Prepayment Rate | Held through Equity Method Investees | Excess MSRs | Minimum
Directly Held
Servicing asset, measurement input	0.074
Prepayment Rate | Held through Equity Method Investees | Excess MSRs | Maximum
Directly Held
Servicing asset, measurement input	0.104
Prepayment Rate | Held through Equity Method Investees | Excess MSRs | Weighted Average
Directly Held
Servicing asset, measurement input	0.087
Delinquency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.000
Delinquency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.800
Delinquency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.050
Delinquency | Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.000
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	0.018
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	0.800
Delinquency | Non-Agency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.212
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	0.800
Delinquency | Ginnie Mae | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.077
Delinquency | Directly Held | Excess MSRs | Minimum
Directly Held
Servicing asset, measurement input	0.003
Delinquency | Directly Held | Excess MSRs | Maximum
Directly Held
Servicing asset, measurement input	0.090
Delinquency | Directly Held | Excess MSRs | Weighted Average
Directly Held
Servicing asset, measurement input	0.046
Delinquency | Held through Equity Method Investees | Excess MSRs | Minimum
Directly Held
Servicing asset, measurement input	0.026
Delinquency | Held through Equity Method Investees | Excess MSRs | Maximum
Directly Held
Servicing asset, measurement input	0.058
Delinquency | Held through Equity Method Investees | Excess MSRs | Weighted Average
Directly Held
Servicing asset, measurement input	0.038
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	0.905
Recapture Rate | Directly Held | Excess MSRs | Weighted Average
Directly Held
Servicing asset, measurement input	0.557
Recapture Rate | Held through Equity Method Investees | Excess MSRs | Minimum
Directly Held
Servicing asset, measurement input	0.450
Recapture Rate | Held through Equity Method Investees | Excess MSRs | Maximum
Directly Held
Servicing asset, measurement input	0.639
Recapture Rate | Held through Equity Method Investees | Excess MSRs | Weighted Average
Directly Held
Servicing asset, measurement input	0.587
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.0001
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.0214
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	0.0125
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Agency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.0028
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Non-Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	0.0001
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Non-Agency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	0.0214
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	0.0073
Mortgage Servicing Amount or Excess Mortgage Servicing Amount (bps) | Ginnie Mae | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	0.0042
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	0.0020
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)	39 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)	28 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)	22 years
Collateral Weighted Average Maturity (Years) | Held through Equity Method Investees | Excess MSRs | Weighted Average
Directly Held
Collateral Weighted Average Maturity (Years)	18 years
Measurement Input, Servicing Cost | Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	6.85
Measurement Input, Servicing Cost | Agency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	7.01
Measurement Input, Servicing Cost | Agency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	6.93
Measurement Input, Servicing Cost | Non-Agency | MSRs and MSR Financing Receivables | Minimum
Directly Held
Servicing asset, measurement input	7.32
Measurement Input, Servicing Cost | Non-Agency | MSRs and MSR Financing Receivables | Maximum
Directly Held
Servicing asset, measurement input	9.62
Measurement Input, Servicing Cost | Non-Agency | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	9.15
Measurement Input, Servicing Cost | Ginnie Mae | MSRs and MSR Financing Receivables | Weighted Average
Directly Held
Servicing asset, measurement input	8.30