INVESTMENTS IN RESIDENTIAL MORTGAGE LOANS - Residential Mortgage Loans Outstanding by Loan Type, Excluding REO (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($) loan	Dec. 31, 2017 USD ($)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Weighted Average Life (Years)	1 year 8 days
Unpaid Principal Balance	$ 84,100,000
Threshold period past due (in days)	60 days
Performing Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Outstanding Face Amount	$ 665,939
Carrying Value	$ 620,303	$ 507,615
Loan Count | loan	8,968
Weighted Average Yield	7.30%
Weighted Average Life (Years)	4 years 11 months 23 days
Floating Rate Loans as a % of Face Amount	16.80%
Loan to Value Ratio (LTV)	79.40%
Weighted Average Delinquency	7.10%
Weighted Average FICO	672
Purchased Credit Deteriorated Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Outstanding Face Amount	$ 211,564
Carrying Value	$ 156,020	183,540
Loan Count | loan	1,828
Weighted Average Yield	7.70%
Weighted Average Life (Years)	3 years 1 month 1 day
Floating Rate Loans as a % of Face Amount	15.90%
Loan to Value Ratio (LTV)	85.60%
Weighted Average Delinquency	75.50%
Weighted Average FICO	595
Residential Mortgage Loans, held-for-investment
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Outstanding Face Amount	$ 877,503
Carrying Value	$ 776,323	691,155
Loan Count | loan	10,796
Weighted Average Yield	7.40%
Weighted Average Life (Years)	4 years 6 months 8 days
Floating Rate Loans as a % of Face Amount	16.60%
Loan to Value Ratio (LTV)	80.90%
Weighted Average Delinquency	23.60%
Weighted Average FICO	653
Reverse Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Outstanding Face Amount	$ 15,271
Carrying Value	$ 6,813	6,870
Loan Count | loan	41
Weighted Average Yield	7.90%
Weighted Average Life (Years)	4 years 10 months 27 days
Floating Rate Loans as a % of Face Amount	10.10%
Loan to Value Ratio (LTV)	135.10%
Weighted Average Delinquency	70.00%
Performing Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Outstanding Face Amount	$ 1,558,201
Carrying Value	$ 1,582,174	1,071,371
Loan Count | loan	13,155
Weighted Average Yield	4.10%
Weighted Average Life (Years)	4 years 3 months 19 days
Floating Rate Loans as a % of Face Amount	55.60%
Loan to Value Ratio (LTV)	62.00%
Weighted Average Delinquency	3.90%
Weighted Average FICO	713
Non-Performing Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Outstanding Face Amount	$ 518,317
Carrying Value	$ 407,316	647,293
Loan Count | loan	4,605
Weighted Average Yield	6.00%
Weighted Average Life (Years)	2 years 10 months 9 days
Floating Rate Loans as a % of Face Amount	17.90%
Loan to Value Ratio (LTV)	89.70%
Weighted Average Delinquency	73.20%
Weighted Average FICO	589
Residential Mortgage Loans, held-for-sale
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Outstanding Face Amount	$ 2,091,789
Carrying Value	$ 1,996,303	1,725,534
Loan Count | loan	17,801
Weighted Average Yield	4.60%
Weighted Average Life (Years)	3 years 11 months 12 days
Floating Rate Loans as a % of Face Amount	45.90%
Loan to Value Ratio (LTV)	69.40%
Weighted Average Delinquency	21.60%
Weighted Average FICO	682
Originated Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Outstanding Face Amount	$ 514,516
Carrying Value	$ 524,863	0
Loan Count | loan	1,948
Weighted Average Yield	4.90%
Weighted Average Life (Years)	28 years 9 months 5 days
Floating Rate Loans as a % of Face Amount	96.00%
Loan to Value Ratio (LTV)	80.90%
Weighted Average Delinquency	4.00%
Weighted Average FICO	717
Residential Mortgage Loans Held-for-Sale, At Fair Value
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Outstanding Face Amount	$ 514,516
Carrying Value	$ 524,863	$ 0
Loan Count | loan	1,948
Weighted Average Yield	4.90%
Weighted Average Life (Years)	28 years 9 months 5 days
Floating Rate Loans as a % of Face Amount	96.00%
Loan to Value Ratio (LTV)	80.90%
Weighted Average Delinquency	4.00%
Weighted Average FICO	717
Reverse Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest in reverse mortgage loans	70.00%
Unpaid principal balance	$ 500
Percentage of loans that have reached a termination event	52.00%
Reverse Mortgage Loans | Nationstar
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest in reverse mortgage loans	30.00%
Performing Loans | Ginnie Mae
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Unpaid Principal Balance	$ 25,700
Non-Performing Loans | Ginnie Mae
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Unpaid Principal Balance	56,500
Non Agency Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Unpaid Principal Balance	$ 124,400