DEBT OBLIGATIONS - Schedule of Debt Obligations (Details) - USD ($)	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Outstanding Face Amount	$ 22,429,761,000
Carrying Value	$ 22,400,516,000	$ 35,636,373,000
Weighted Average Funding Cost	1.93%
Weighted Average Life (Years)	2 years 3 months 18 days
MSR purchase price holdback	$ 33,195,000	68,668,000
Secured Notes and Bonds Payable | Mr. Cooper
Debt Instrument [Line Items]
Outstanding Face Amount	$ 989,100,000
Repurchase Agreements
Debt Instrument [Line Items]
Weighted Average Funding Cost	3.94%
Weighted Average Life (Years)	1 year 3 months 18 days
Secured Financing Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	$ 14,673,179,000
Carrying Value	$ 14,666,868,000	27,916,225,000
Weighted Average Funding Cost	1.05%
Weighted Average Life (Years)	4 months 24 days
MSR purchase price holdback	$ 19,500,000
Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	7,756,582,000
Carrying Value	$ 7,733,648,000	7,720,148,000
Weighted Average Funding Cost	3.60%
Weighted Average Life (Years)	6 years 1 month 6 days
Warehouse Credit Facilities-Residential Mortgage Loans | Repurchase Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	$ 3,759,627,000
Carrying Value	$ 3,754,803,000	5,053,207,000
Weighted Average Funding Cost	2.50%
Weighted Average Life (Years)	1 year
Repurchase agreements	$ 270,700,000
Interest rate	4.40%
Warehouse Credit Facilities-Residential Mortgage Loans | Repurchase Agreements | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	17 years 1 month 6 days
Outstanding Face of Collateral	$ 4,156,437,000
Amortized Cost Basis of Collateral	4,250,005,000
Carrying Value of Collateral	4,215,066,000
Agency RMBS | Repurchase Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	9,958,246,000
Carrying Value	$ 9,958,246,000	15,481,677,000
Weighted Average Funding Cost	0.20%
Weighted Average Life (Years)	2 months 12 days
Agency RMBS | Repurchase Agreements | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	3 years 9 months 18 days
Outstanding Face of Collateral	$ 9,930,973,000
Amortized Cost Basis of Collateral	10,285,282,000
Carrying Value of Collateral	10,361,950,000
Non-Agency RMBS | Repurchase Agreements | Retained Servicer Advance and Consumer Bonds
Debt Instrument [Line Items]
Carrying Value	30,400,000
Non-Agency RMBS | Repurchase Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	952,323,000
Carrying Value	$ 950,836,000	7,317,519,000
Weighted Average Funding Cost	4.10%
Non-Agency RMBS | Repurchase Agreements | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	6 years
Outstanding Face of Collateral	$ 18,999,108,000
Amortized Cost Basis of Collateral	1,730,072,000
Carrying Value of Collateral	1,734,798,000
Non-Agency RMBS | Repurchase Agreements | Collateral | Retained Servicer Advance and Consumer Bonds
Debt Instrument [Line Items]
Carrying Value	37,300,000
Real Estate Owned | Repurchase Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	2,983,000
Carrying Value	2,983,000	63,822,000
Real Estate Owned | Repurchase Agreements | Collateral
Debt Instrument [Line Items]
Carrying Value of Collateral	3,796,000
Excess MSRs
Debt Instrument [Line Items]
Carrying Value	264,980,000	217,300,000
Excess MSRs | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	264,980,000
Carrying Value	$ 264,980,000	217,300,000
Weighted Average Funding Cost	3.91%
Weighted Average Life (Years)	1 year 1 month 6 days
Excess MSRs | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	6 years
Outstanding Face of Collateral	$ 107,584,509,000
Amortized Cost Basis of Collateral	333,874,000
Carrying Value of Collateral	421,907,000
MSRs | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	2,794,108,000
Carrying Value	$ 2,786,144,000	2,640,036,000
Weighted Average Funding Cost	4.57%
Weighted Average Life (Years)	2 years 3 months 18 days
MSRs | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	5 years 9 months 18 days
Outstanding Face of Collateral	$ 444,177,336,000
Amortized Cost Basis of Collateral	4,645,075,000
Carrying Value of Collateral	4,675,648,000
Servicer Advance Investments | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	412,538,000
Carrying Value	$ 412,538,000	581,777,000
Weighted Average Funding Cost	2.27%
Weighted Average Life (Years)	7 months 6 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	$ 434,998,000
Amortized Cost Basis of Collateral	510,995,000
Carrying Value of Collateral	$ 535,760,000
Servicer Advances | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Variable interest rate spread	1.38%
Servicer Advances | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument [Line Items]
Variable interest rate spread	1.85%
Servicer Advances | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 2,502,158,000
Carrying Value	$ 2,492,239,000	2,599,895,000
Weighted Average Funding Cost	2.84%
Weighted Average Life (Years)	1 year 10 months 24 days
Face amount of debt at fixed rate	$ 1,900,000,000
Servicer Advances | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	8 months 12 days
Outstanding Face of Collateral	$ 2,747,433,000
Amortized Cost Basis of Collateral	2,857,040,000
Carrying Value of Collateral	2,857,040,000
Residential Mortgage | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	1,103,847,000
Carrying Value	$ 1,096,638,000	864,451,000
Weighted Average Funding Cost	4.26%
Weighted Average Life (Years)	30 years 1 month 6 days
Residential Mortgage | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	4 years 1 month 6 days
Outstanding Face of Collateral	$ 1,656,351,000
Amortized Cost Basis of Collateral	1,588,739,000
Carrying Value of Collateral	1,413,258,000
Consumer Loans
Debt Instrument [Line Items]
Carrying Value	681,109,000	816,689,000
Consumer Loans | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	678,951,000
Carrying Value	$ 681,109,000	$ 816,689,000
Weighted Average Funding Cost	2.03%
Weighted Average Life (Years)	3 years
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	$ 663,047,000
Amortized Cost Basis of Collateral	718,287,000
Carrying Value of Collateral	718,287,000
2.50% Secured Corporate Note | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 70,200,000
2.50% Secured Corporate Note | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Variable interest rate spread	2.50%
3.50% Secured Corporate Note | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Outstanding Face Amount	$ 194,700,000
Variable interest rate spread	3.50%
4.50% Agency MSR Secured Note And Bond Payable | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 326,100,000
4.50% Agency MSR Secured Note And Bond Payable | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Outstanding Face Amount	$ 933,000,000.0
Variable interest rate spread	4.50%
2.50% Agency MSR Secured Note | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 37,400,000
2.50% Agency MSR Secured Note | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Variable interest rate spread	2.50%
3.55% To 5.44% Agency MSR Secured Notes And Bonds Payable | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 1,497,600,000
3.55% To 5.44% Agency MSR Secured Notes And Bonds Payable | Secured Notes and Bonds Payable | Minimum
Debt Instrument [Line Items]
Outstanding Face Amount	0.0355
3.55% To 5.44% Agency MSR Secured Notes And Bonds Payable | Secured Notes and Bonds Payable | Maximum
Debt Instrument [Line Items]
Outstanding Face Amount	0.0544
2.88% Residential Mortgage Loans | Secured Notes and Bonds Payable | Mr. Cooper
Debt Instrument [Line Items]
Collateral amount	$ 1,400,000
2.88% Residential Mortgage Loans | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR) | Mr. Cooper
Debt Instrument [Line Items]
Variable interest rate spread	2.88%
3.72% Asset-Backed Notes | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 75,100,000
3.72% Asset-Backed Notes | Secured Notes and Bonds Payable | Maximum
Debt Instrument [Line Items]
Weighted Average Funding Cost	3.72%
6.63% Asset-Backed Notes | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 165,500,000
Interest rate	6.63%
3.23% To 5.00% Asset-Backed Notes | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 0.0323
3.23% To 5.00% Asset-Backed Notes | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR)
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	1.97%
UPB of Underlying Mortgages	$ 610,000,000.0
Consumer Loan, UPB Class B | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Interest rate	2.66%
UPB of Underlying Mortgages	$ 53,000,000.0