INVESTMENTS IN RESIDENTIAL MORTGAGE LOANS - Performing Loans Past Due (Details) - Residential Portfolio Segment - Performing Loans	Dec. 31, 2018
Investment [Line Items]
Delinquency Status	100.00%
Current
Investment [Line Items]
Delinquency Status	83.30%
30-59
Investment [Line Items]
Delinquency Status	7.40%
60-89
Investment [Line Items]
Delinquency Status	2.20%
90-119
Investment [Line Items]
Delinquency Status	0.80%
120
Investment [Line Items]
Delinquency Status	6.30%