THE FREMF TRUSTS - Narrative (Details) - FREMF Trusts - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Investment in Multi-Family MBS, carrying value	$ 20,339,325	$ 21,695,098
Multi-family mortgage loans held in securitization trusts, unpaid principal balance	1,073,365,225	1,078,622,737
Multi-family securitized debt obligations, unpaid principal balance	$ 1,073,365,225	$ 1,078,622,737

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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