DEBT OBLIGATIONS - Schedule of Debt Obligations (Details) - USD ($)	6 Months Ended
	Jun. 30, 2021	May 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Outstanding Face Amount	$ 28,618,727,000
Carrying Value	$ 28,594,868,000		$ 25,191,875,000
Weighted Average Funding Cost	1.35%
Weighted Average Life (Years)	10 months 24 days
MSR purchase price holdback	$ 24,897,000		44,623,000
Secured Notes and Bonds Payable | Mr. Cooper
Debt Instrument [Line Items]
Outstanding Face Amount	5,900,000
Secured Financing Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	21,291,164,000
Carrying Value	$ 21,290,862,000		17,547,680,000
Weighted Average Funding Cost	0.81%
Weighted Average Life (Years)	2 months 12 days
MSR purchase price holdback	$ 73,500,000
Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	7,327,563,000
Carrying Value	$ 7,304,006,000		7,644,195,000
Weighted Average Funding Cost	2.91%
Weighted Average Life (Years)	3 years
Securitization Notes Payable | Variable Interest Entity, Primary Beneficiary
Debt Instrument [Line Items]
Outstanding Face Amount		$ 750,000,000.0
Real Estate Owned
Debt Instrument [Line Items]
Weighted Average Funding Cost	2.83%
Warehouse Credit Facilities-Residential Mortgage Loans | Repurchase Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	$ 5,595,304,000
Carrying Value	$ 5,595,001,000		4,039,564,000
Weighted Average Funding Cost	2.18%
Weighted Average Life (Years)	7 months 6 days
Repurchase agreements	$ 234,600,000
Interest rate	4.40%
Warehouse Credit Facilities-Residential Mortgage Loans | Repurchase Agreements | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	24 years 4 months 24 days
Outstanding Face of Collateral	$ 6,137,572,000
Amortized Cost Basis of Collateral	6,062,869,000
Carrying Value of Collateral	6,108,837,000
Agency RMBS | Secured Financing Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	14,935,294,000
Carrying Value	$ 14,935,294,000		12,682,427,000
Weighted Average Funding Cost	0.17%
Weighted Average Life (Years)	1 month 6 days
Agency RMBS | Secured Financing Agreements | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	1 year
Outstanding Face of Collateral	$ 14,771,792,000
Amortized Cost Basis of Collateral	15,278,052,000
Carrying Value of Collateral	15,059,319,000
Non-Agency RMBS | Repurchase Agreements | Retained Servicer Advance and Consumer Bonds
Debt Instrument [Line Items]
Carrying Value	13,600,000
Non-Agency RMBS | Repurchase Agreements | Collateral | Retained Servicer Advance and Consumer Bonds
Debt Instrument [Line Items]
Carrying Value	18,000,000.0
Non-Agency RMBS | Secured Financing Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	691,034,000
Carrying Value	$ 691,034,000		817,209,000
Weighted Average Funding Cost	3.28%
Weighted Average Life (Years)	0 years
Non-Agency RMBS | Secured Financing Agreements | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	8 months 12 days
Outstanding Face of Collateral	$ 13,954,357,000
Amortized Cost Basis of Collateral	1,113,243,000
Carrying Value of Collateral	1,200,347,000
Real Estate Owned | Secured Financing Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	69,532,000
Carrying Value	$ 69,533,000		8,480,000
Weighted Average Life (Years)	2 years 10 months 24 days
Real Estate Owned | Secured Financing Agreements | Single Family Rental Collateralized Notes
Debt Instrument [Line Items]
Outstanding Face Amount	$ 45,400,000
Real Estate Owned | Secured Financing Agreements | Collateral
Debt Instrument [Line Items]
Carrying Value of Collateral	83,916,000
Excess MSRs
Debt Instrument [Line Items]
Carrying Value	264,277,000		275,088,000
Excess MSRs | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	264,277,000
Carrying Value	$ 264,277,000		275,088,000
Weighted Average Funding Cost	4.36%
Weighted Average Life (Years)	3 years 2 months 12 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	$ 89,755,059,000
Amortized Cost Basis of Collateral	293,976,000
Carrying Value of Collateral	365,997,000
MSRs | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	2,505,820,000
Carrying Value	$ 2,494,717,000		2,691,791,000
Weighted Average Funding Cost	4.06%
Weighted Average Life (Years)	3 years 6 months
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	$ 388,124,130,000
Amortized Cost Basis of Collateral	4,363,971,000
Carrying Value of Collateral	4,701,128,000
Servicer Advance Investments | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	402,039,000
Carrying Value	$ 401,166,000		423,144,000
Weighted Average Funding Cost	1.33%
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 1 month 6 days
Outstanding Face of Collateral	$ 420,537,000
Amortized Cost Basis of Collateral	482,308,000
Carrying Value of Collateral	$ 502,533,000
Servicer Advances | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Variable interest rate spread	1.10%
Servicer Advances | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument [Line Items]
Variable interest rate spread	3.90%
Servicer Advances | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 2,411,938,000
Carrying Value	$ 2,405,718,000		2,585,575,000
Weighted Average Funding Cost	2.32%
Weighted Average Life (Years)	1 year 8 months 12 days
Face amount of debt at fixed rate	$ 2,000,000,000.0
Servicer Advances | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	8 months 12 days
Outstanding Face of Collateral	$ 2,709,963,000
Amortized Cost Basis of Collateral	2,719,410,000
Carrying Value of Collateral	2,719,410,000
Residential Mortgage Loans | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	1,208,383,000
Carrying Value	$ 1,197,064,000		1,039,838,000
Weighted Average Funding Cost	2.30%
Weighted Average Life (Years)	4 years 8 months 12 days
Residential Mortgage Loans | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	18 years 6 months
Outstanding Face of Collateral	$ 1,326,788,000
Amortized Cost Basis of Collateral	1,461,742,000
Carrying Value of Collateral	1,449,245,000
Consumer Loans
Debt Instrument [Line Items]
Carrying Value	541,064,000		628,759,000
Consumer Loans | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	535,106,000
Carrying Value	$ 541,064,000		$ 628,759,000
Weighted Average Funding Cost	2.04%
Weighted Average Life (Years)	3 years 6 months
Consumer Loans | Secured Notes and Bonds Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	3 years 3 months 18 days
Outstanding Face of Collateral	$ 527,541,000
Amortized Cost Basis of Collateral	537,287,000
Carrying Value of Collateral	591,248,000
4.40% Secured Corporate Note | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 264,300,000
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	$ 328,900,000
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	$ 239,900,000
3.0% To 5.4% Public Notes | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	1,937,000,000.0
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	$ 38,700,000
3.7% Asset-Backed Notes | Secured Notes and Bonds Payable | Maximum
Debt Instrument [Line Items]
Weighted Average Funding Cost	3.70%
6.2% Asset-Backed Notes | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 68,800,000
Interest rate	6.20%
3.6% To 5.00% Asset-Backed Notes | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 244,500,000
3.6% 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	3.60%
3.6% 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%
Residential mortgage loan UPB	$ 482,100,000
Consumer Loan, UPB Class B | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Interest rate	2.70%
Residential mortgage loan UPB	$ 53,000,000.0
2.8% Asset-Backed Notes | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 100,500,000
Interest rate	2.80%
Revolving Warehouse Facility Backed Notes | Secured Notes and Bonds Payable | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Variable interest rate spread	1.10%
Revolving Warehouse Facility Backed Notes | Secured Notes and Bonds Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 750,000,000.0