COMMERCIAL MORTGAGE LOANS HELD-FOR-INVESTMENT - Loan Portfolio Activity (Details) - USD ($)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Loans Receivable Held-For-Investment, Net, Reconciliation To Cash Flow [Roll Forward]
Balance at December 31, 2018	$ 555,172,891
Purchases, net	64,612,349	$ 0
Proceeds from principal repayments	(34,014,437)	$ 0
Balance at March 31, 2019	585,770,803
Commercial real estate portfolio segment
Loans Receivable Held-For-Investment, Net, Reconciliation To Cash Flow [Roll Forward]
Balance at December 31, 2018	555,172,891
Purchases, net	64,612,349
Proceeds from principal repayments	(34,014,437)
Balance at March 31, 2019	$ 585,770,803

Loans Receivable Held-For-Investment, Net, Reconciliation To Cash Flow [Roll Forward]

No definition available.

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- Definition

Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

The cash outflow associated with purchasing loans held for investment purposes during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

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- Definition

The cash inflow from repayments of the balance excluding interest (principal) on loans receivable and leases held for investment purposes.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3179-108585

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- Details

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