INVESTMENTS IN RESIDENTIAL MORTGAGE LOANS - Required Payments Receivable, Cash Flows Expected to be Collected, and Fair Value at Acquisition Date for Loans Acquired during the Period (Details) - PCD Loans $ in Thousands	Dec. 31, 2018 USD ($)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Contractually Required Payments Receivable	$ 65,902
Cash Flows Expected to be Collected	45,429
Fair Value	$ 29,785