DEBT OBLIGATIONS - Schedule of Debt Obligations (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Outstanding Face Amount	$ 15,099,119,000
Carrying Value	$ 15,084,995,000	$ 13,181,236,000
Weighted Average Funding Cost	3.17%
Weighted Average Life (Years)	1 year 3 months 1 day
Interest payable	$ 30,075,000	23,108,000
Agency RMBS | Repurchase Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	1,846,934,000
Carrying Value	$ 1,846,934,000	1,764,760,000
Weighted Average Funding Cost	1.35%
Weighted Average Life (Years)	1 month 19 days
Agency RMBS | Repurchase Agreements | Trade And Other Receivables
Debt Instrument [Line Items]
Collateral amount	$ 1,800,000,000
Agency RMBS | Repurchase Agreements | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	3 months 23 days
Outstanding Face of Collateral	$ 1,845,992,000
Amortized Cost Basis of Collateral	1,905,003,000
Carrying Value of Collateral	1,907,360,000
Non-Agency RMBS | Repurchase Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	4,316,544,000
Carrying Value	$ 4,316,544,000	2,654,242,000
Weighted Average Funding Cost	2.76%
Weighted Average Life (Years)	21 days
Non-Agency RMBS | Repurchase Agreements | Retained Servicer Advance and Consumer Bonds
Debt Instrument [Line Items]
Carrying Value	$ 160,300,000
Non-Agency RMBS | Repurchase Agreements | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	7 years 8 months 15 days
Outstanding Face of Collateral	$ 11,050,796,000
Amortized Cost Basis of Collateral	5,024,799,000
Carrying Value of Collateral	5,404,713,000
Residential Mortgage | Repurchase Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	1,584,033,000
Carrying Value	$ 1,581,980,000	686,412,000
Weighted Average Funding Cost	3.75%
Weighted Average Life (Years)	3 months 12 days
Residential Mortgage | Repurchase Agreements | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	4 years 3 months 11 days
Outstanding Face of Collateral	$ 2,136,065,000
Amortized Cost Basis of Collateral	1,907,212,000
Carrying Value of Collateral	1,890,819,000
Residential Mortgage | Notes Payable
Debt Instrument [Line Items]
Outstanding Face Amount	143,207,000
Carrying Value	$ 143,207,000	8,271,000
Weighted Average Funding Cost	3.61%
Weighted Average Life (Years)	2 years 6 months 7 days
Residential Mortgage | Notes Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	7 years 10 months 22 days
Outstanding Face of Collateral	$ 234,686,000
Amortized Cost Basis of Collateral	184,639,000
Carrying Value of Collateral	184,639,000
Real Estate Owned | Repurchase Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	102,703,000
Carrying Value	$ 102,570,000	85,217,000
Weighted Average Funding Cost	3.57%
Weighted Average Life (Years)	6 months 4 days
Real Estate Owned | Repurchase Agreements | Collateral
Debt Instrument [Line Items]
Carrying Value of Collateral	$ 145,939,000
Real Estate Owned | Notes Payable
Debt Instrument [Line Items]
Outstanding Face Amount	2,974,000
Carrying Value	$ 2,974,000	3,106,000
Weighted Average Funding Cost	3.78%
Weighted Average Life (Years)	1 year 29 days
Real Estate Owned | Notes Payable | Collateral
Debt Instrument [Line Items]
Carrying Value of Collateral	$ 2,792,000
Total Repurchase Agreements | Repurchase Agreements
Debt Instrument [Line Items]
Outstanding Face Amount	7,850,214,000
Carrying Value	$ 7,848,028,000	5,190,631,000
Weighted Average Funding Cost	2.64%
Weighted Average Life (Years)	1 month 16 days
Interest payable	$ 18,400,000
Secured Corporate Note | Notes Payable
Debt Instrument [Line Items]
Outstanding Face Amount	583,686,000
Carrying Value	$ 583,415,000	729,145,000
Weighted Average Funding Cost	4.98%
Weighted Average Life (Years)	2 years 10 months 17 days
Secured Corporate Note | Notes Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	5 years 10 months 10 days
Outstanding Face of Collateral	$ 263,232,259,000
Amortized Cost Basis of Collateral	1,085,585,000
Carrying Value of Collateral	1,212,791,000
MSRs | Notes Payable
Debt Instrument [Line Items]
Outstanding Face Amount	1,097,085,000
Carrying Value	$ 1,096,380,000	0
Weighted Average Funding Cost	5.28%
Weighted Average Life (Years)	2 years 3 months 16 days
MSRs | Notes Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	6 years 2 months 19 days
Outstanding Face of Collateral	$ 223,999,150,000
Amortized Cost Basis of Collateral	1,949,608,000
Carrying Value of Collateral	2,145,609,000
Servicer Advances
Debt Instrument [Line Items]
Carrying Value	4,073,283,000	5,549,872,000
Servicer Advances | Notes Payable
Debt Instrument [Line Items]
Outstanding Face Amount	4,081,010,000
Carrying Value	$ 4,073,283,000	5,549,872,000
Weighted Average Funding Cost	3.29%
Weighted Average Life (Years)	2 years 2 months 21 days
Face amount of debt at fixed rate	$ 3,800,000,000
Servicer Advances | Notes Payable | London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Variable interest rate spread	1.85523%
Servicer Advances | Notes Payable | London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument [Line Items]
Variable interest rate spread	2.42187%
Servicer Advances | Notes Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	4 years 5 months 22 days
Outstanding Face of Collateral	$ 4,297,775,000
Amortized Cost Basis of Collateral	4,591,210,000
Carrying Value of Collateral	4,680,637,000
Consumer Loans
Debt Instrument [Line Items]
Carrying Value	1,337,708,000	1,700,211,000
Consumer Loans | Notes Payable
Debt Instrument [Line Items]
Outstanding Face Amount	1,340,943,000
Carrying Value	$ 1,337,708,000	1,700,211,000
Weighted Average Funding Cost	3.35%
Weighted Average Life (Years)	3 years 2 months 15 days
Consumer Loans | Notes Payable | Collateral
Debt Instrument [Line Items]
Weighted Average Life (Years)	3 years 6 months 14 days
Outstanding Face of Collateral	$ 1,472,792,000
Amortized Cost Basis of Collateral	1,473,353,000
Carrying Value of Collateral	1,467,752,000
Total Notes Payable | Notes Payable
Debt Instrument [Line Items]
Outstanding Face Amount	7,248,905,000
Carrying Value	$ 7,236,967,000	$ 7,990,605,000
Weighted Average Funding Cost	3.75%
Weighted Average Life (Years)	2 years 5 months 21 days
3.75% Secured Corporate Note | Secured Debt
Debt Instrument [Line Items]
Outstanding Face Amount	$ 213,700,000
3.75% Secured Corporate Note | Secured Debt | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Variable interest rate spread	3.75%
3.75% Secured Corporate Loan | Secured Debt
Debt Instrument [Line Items]
Outstanding Face Amount	$ 370,000,000
4.25% Agency MSR Secured Note | Secured Debt
Debt Instrument [Line Items]
Outstanding Face Amount	$ 290,000,000
4.25% Agency MSR Secured Note | Secured Debt | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Variable interest rate spread	4.25%
3.75% Agency MSR Secured Note | Secured Debt
Debt Instrument [Line Items]
Outstanding Face Amount	$ 232,870,959.12000000
3.75% Agency MSR Secured Note | Secured Debt | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Variable interest rate spread	3.75%
3.50% Agency MSR Secured Note | Secured Debt
Debt Instrument [Line Items]
Outstanding Face Amount	$ 74,000,000
3.50% Agency MSR Secured Note | Secured Debt | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Variable interest rate spread	3.50%
4.00% Agency MSR Secured Note | Secured Debt
Debt Instrument [Line Items]
Outstanding Face Amount	$ 500,200,000
4.00% Agency MSR Secured Note | Secured Debt | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Variable interest rate spread	4.00%
2.88% Residential Mortgage Loans | Notes Payable | Nationstar
Debt Instrument [Line Items]
Outstanding Face Amount	$ 10,800,000
2.88% Residential Mortgage Loans | Notes Payable | London Interbank Offered Rate (LIBOR) | Nationstar
Debt Instrument [Line Items]
Variable interest rate spread	2.875%
3.60% Residential Mortgage Asset-backed Notes | Notes Payable
Debt Instrument [Line Items]
Outstanding Face Amount	$ 135,400,000
Interest rate, stated percentage	3.60%
Consumer Loan, UPB Class A | Secured Debt
Debt Instrument [Line Items]
Interest rate, stated percentage	3.05%
UPB of Underlying Mortgages	$ 1,000,000,000
Consumer Loan, UPB Class B | Secured Debt
Debt Instrument [Line Items]
Interest rate, stated percentage	4.10%
UPB of Underlying Mortgages	$ 210,800,000
Consumer Loan, UPB Class C-1 | Secured Debt
Debt Instrument [Line Items]
Interest rate, stated percentage	5.63%
UPB of Underlying Mortgages	$ 18,300,000
Consumer Loan, UPB Class C-2 | Secured Debt
Debt Instrument [Line Items]
Interest rate, stated percentage	5.63%
UPB of Underlying Mortgages	$ 18,300,000
4.00% Consumer Loans | Secured Debt
Debt Instrument [Line Items]
Outstanding Face Amount	$ 86,300,000
Interest rate, stated percentage	4.00%