Quarterly report pursuant to Section 13 or 15(d)

INVESTMENTS IN RESIDENTIAL MORTGAGE LOANS - Geographic Distribution of the Underlying Residential Mortgage Loans (Details)

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INVESTMENTS IN RESIDENTIAL MORTGAGE LOANS - Geographic Distribution of the Underlying Residential Mortgage Loans (Details) - Residential Mortgage Loans
Sep. 30, 2018
Dec. 31, 2017
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]    
Percentage of Total Outstanding Unpaid Principal Amount 100.00% 100.00%
California    
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]    
Percentage of Total Outstanding Unpaid Principal Amount 19.30% 9.10%
New York    
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]    
Percentage of Total Outstanding Unpaid Principal Amount 12.00% 12.80%
Texas    
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]    
Percentage of Total Outstanding Unpaid Principal Amount 6.30% 8.20%
Texas    
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]    
Percentage of Total Outstanding Unpaid Principal Amount 5.60% 6.60%
New Jersey    
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]    
Percentage of Total Outstanding Unpaid Principal Amount 5.20% 5.20%
Pennsylvania    
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]    
Percentage of Total Outstanding Unpaid Principal Amount 3.20% 3.90%
Pennsylvania    
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]    
Percentage of Total Outstanding Unpaid Principal Amount 2.90% 3.40%
Massachusetts    
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]    
Percentage of Total Outstanding Unpaid Principal Amount 2.80% 2.70%
Maryland    
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]    
Percentage of Total Outstanding Unpaid Principal Amount 2.40% 2.70%
Washington    
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]    
Percentage of Total Outstanding Unpaid Principal Amount 1.70% 1.70%
Other U.S.    
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]    
Percentage of Total Outstanding Unpaid Principal Amount 38.60% 43.70%