DEBT OBLIGATIONS - Schedule of Debt Obligations (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Outstanding Face Amount	$ 26,651,603,000
Carrying Value	$ 26,630,335,000	$ 25,191,875,000
Weighted Average Funding Cost	1.50%
Weighted Average Life (Years)	1 year 6 months
MSR purchase price holdback	$ 37,345,000	44,623,000
Secured Notes and Bonds Payable | Mr. Cooper
Debt Instrument [Line Items]
Outstanding Face Amount	$ 5,800,000
Repurchase Agreements
Debt Instrument [Line Items]
Weighted Average Funding Cost	2.60%
Secured Financing Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	$ 19,524,439,000
Carrying Value	$ 19,522,460,000	17,547,680,000
Weighted Average Funding Cost	0.86%
Weighted Average Life (Years)	6 months
MSR purchase price holdback	$ 56,400,000
Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	7,127,164,000
Carrying Value	$ 7,107,875,000	7,644,195,000
Weighted Average Funding Cost	3.27%
Weighted Average Life (Years)	4 years 3 months 18 days
Warehouse Credit Facilities-Residential Mortgage Loans | Repurchase Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	$ 5,133,435,000
Carrying Value	$ 5,131,682,000	4,039,564,000
Weighted Average Funding Cost	2.18%
Repurchase agreements	$ 247,700,000
Interest rate	4.40%
Warehouse Credit Facilities-Residential Mortgage Loans | Repurchase Agreements | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	20 years
Outstanding Face of Collateral	$ 5,539,834,000
Amortized Cost Basis of Collateral	5,601,036,000
Carrying Value of Collateral	$ 5,562,750,000
Warehouse Credit Facilities-Residential Mortgage Loans | Secured Financing Agreements
Debt Instrument [Line Items]
Weighted Average Life (Years)	7 months 6 days
Agency RMBS | Repurchase Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	$ 13,641,520,000
Carrying Value	$ 13,641,520,000	12,682,427,000
Weighted Average Funding Cost	0.23%
Agency RMBS | Repurchase Agreements | Collateral
Debt Instrument [Line Items]
Outstanding Face of Collateral	$ 13,443,593,000
Amortized Cost Basis of Collateral	13,956,269,000
Carrying Value of Collateral	$ 13,558,231,000
Agency RMBS | Secured Financing Agreements
Debt Instrument [Line Items]
Weighted Average Life (Years)	4 months 24 days
Agency RMBS | Secured Financing Agreements | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	1 year
Non-Agency RMBS | Repurchase Agreements | Retained Servicer Advance and Consumer Bonds
Debt Instrument [Line Items]
Carrying Value	$ 24,100,000
Non-Agency RMBS | Repurchase Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	740,770,000
Carrying Value	$ 740,544,000	817,209,000
Weighted Average Funding Cost	3.33%
Non-Agency RMBS | Repurchase Agreements | Collateral
Debt Instrument [Line Items]
Outstanding Face of Collateral	$ 15,722,106,000
Amortized Cost Basis of Collateral	1,247,027,000
Carrying Value of Collateral	1,304,584,000
Non-Agency RMBS | Repurchase Agreements | Collateral | Retained Servicer Advance and Consumer Bonds
Debt Instrument [Line Items]
Carrying Value	$ 33,100,000
Non-Agency RMBS | Secured Financing Agreements
Debt Instrument [Line Items]
Weighted Average Life (Years)	6 months
Non-Agency RMBS | Secured Financing Agreements | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	8 months 12 days
Real Estate Owned | Repurchase Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	$ 8,714,000
Carrying Value	8,714,000	8,480,000
Real Estate Owned | Repurchase Agreements | Collateral
Debt Instrument [Line Items]
Carrying Value of Collateral	$ 11,580,000
Real Estate Owned | Secured Financing Agreements
Debt Instrument [Line Items]
Weighted Average Life (Years)	1 year 9 months 18 days
Excess MSRs
Debt Instrument [Line Items]
Carrying Value	$ 265,899,000	275,088,000
Excess MSRs | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	265,899,000
Carrying Value	$ 265,899,000	275,088,000
Weighted Average Funding Cost	4.36%
Weighted Average Life (Years)	3 years 4 months 24 days
Excess MSRs | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	6 years 2 months 12 days
Outstanding Face of Collateral	$ 95,393,278,000
Amortized Cost Basis of Collateral	315,399,000
Carrying Value of Collateral	390,631,000
MSRs | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	2,696,137,000
Carrying Value	$ 2,685,492,000	2,691,791,000
Weighted Average Funding Cost	4.25%
Weighted Average Life (Years)	3 years 3 months 18 days
MSRs | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	6 years 2 months 12 days
Outstanding Face of Collateral	$ 385,377,861,000
Amortized Cost Basis of Collateral	4,240,151,000
Carrying Value of Collateral	4,717,694,000
Servicer Advance Investments | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	403,570,000
Carrying Value	$ 402,691,000	423,144,000
Weighted Average Funding Cost	1.42%
Weighted Average Life (Years)	1 year 3 months 18 days
Servicer Advance Investments | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	6 years 3 months 18 days
Outstanding Face of Collateral	$ 440,306,000
Amortized Cost Basis of Collateral	492,831,000
Carrying Value of Collateral	$ 517,558,000
Servicer Advance Investments | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Variable interest rate spread	1.40%
Servicer Advance Investments | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument [Line Items]
Variable interest rate spread	3.90%
Servicer Advance Investments | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 2,494,763,000
Carrying Value	$ 2,487,465,000	2,585,575,000
Weighted Average Funding Cost	2.43%
Weighted Average Life (Years)	1 year 7 months 6 days
Face amount of debt at fixed rate	$ 2,000,000,000.0
Servicer Advance Investments | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Outstanding Face of Collateral	2,898,656,000
Amortized Cost Basis of Collateral	2,895,073,000
Carrying Value of Collateral	2,895,073,000
Residential Mortgage Loans | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	682,847,000
Carrying Value	$ 675,317,000	1,039,838,000
Weighted Average Funding Cost	4.18%
Weighted Average Life (Years)	20 years 4 months 24 days
Residential Mortgage Loans | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	4 years 2 months 12 days
Outstanding Face of Collateral	$ 1,019,812,000
Amortized Cost Basis of Collateral	998,328,000
Carrying Value of Collateral	934,291,000
Consumer Loans
Debt Instrument [Line Items]
Carrying Value	591,011,000	628,759,000
Consumer Loans | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	583,948,000
Carrying Value	$ 591,011,000	628,759,000
Weighted Average Funding Cost	2.03%
Weighted Average Life (Years)	3 years 4 months 24 days
Consumer Loans | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	3 years 7 months 6 days
Outstanding Face of Collateral	$ 575,267,000
Amortized Cost Basis of Collateral	584,632,000
Carrying Value of Collateral	637,264,000
4.40% Secured Corporate Note | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 265,900,000
4.40% Secured Corporate Note | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Variable interest rate spread	4.40%
3.30% Agency MSR Secured Note And Bond Payable | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Outstanding Face Amount	$ 373,900,000
Variable interest rate spread	3.30%
3.9% Agency MSR | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Variable interest rate spread	3.90%
3.9% Agency MSR | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 394,900,000
3.0% To 5.4% Public Notes | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	1,927,300,000
3.0% To 5.4% Public Notes | Secured Notes and Bonds Payable | Minimum
Debt Instrument [Line Items]
Outstanding Face Amount	0.030
3.0% To 5.4% Public Notes | Secured Notes and Bonds Payable | Maximum
Debt Instrument [Line Items]
Outstanding Face Amount	0.054
2.9% Residential Mortgage Loans | Secured Notes and Bonds Payable | Mr. Cooper
Debt Instrument [Line Items]
Collateral amount	$ 1,600,000
2.9% Residential Mortgage Loans | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR) | Mr. Cooper
Debt Instrument [Line Items]
Variable interest rate spread	2.90%
3.7% Asset-Backed Notes | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 50,700,000
3.7% Asset-Backed Notes | Secured Notes and Bonds Payable | Maximum
Debt Instrument [Line Items]
Weighted Average Funding Cost	3.70%
6.6% Asset-Backed Notes | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 139,200,000
Interest rate	6.60%
3.2% To 5.00% Asset-Backed Notes | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 466,500,000
3.2% To 5.00% Asset-Backed Notes | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Variable interest rate spread	3.20%
3.2% To 5.00% Asset-Backed Notes | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument [Line Items]
Variable interest rate spread	5.00%
Consumer Loan, UPB Class A | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Interest rate	2.00%
UPB of Underlying Mortgages	$ 530,900,000
Consumer Loan, UPB Class B | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Interest rate	2.70%
UPB of Underlying Mortgages	$ 53,000,000.0
Servicer advances
Debt Instrument [Line Items]
Carrying Value	$ 2,890,156,000	$ 3,008,719,000
Servicer advances | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	8 months 12 days