FINANCIAL INSTRUMENTS FINANCIAL INSTRUMENTS - Fair Value Information on Financial Instruments (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 73,380,534	$ 34,347,339
Restricted cash	7,932,233	11,275,263
Available-for-sale securities	0	1,234,522,000
Total assets	459,532,284	2,612,541,116
Collateralized loan obligations	287,738,948	0
Total liabilities	309,497,324	2,466,749,839
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	73,380,534	34,347,339
Restricted cash	7,932,233	11,275,263
Available-for-sale securities		1,234,522,000
Commercial mortgage loans held-for-investment, at amortized cost	326,883,547
Total assets	408,196,314	45,622,602
Collateralized loan obligations	287,738,948
Total liabilities	287,738,948	1,234,522,000
Face Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	73,380,534	34,347,339
Restricted cash	7,932,233	11,275,263
Available-for-sale securities		1,234,522,000
Commercial mortgage loans held-for-investment, at amortized cost	326,883,547
Total assets	408,196,314	45,622,602
Collateralized loan obligations	290,732,000
Total liabilities	290,732,000	1,234,522,000
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	73,380,534	34,347,339
Restricted cash	7,932,233	11,275,263
Available-for-sale securities		1,234,522,000
Commercial mortgage loans held-for-investment, at amortized cost	326,883,547
Total assets	408,196,314	45,622,602
Collateralized loan obligations	290,761,639
Total liabilities	$ 290,761,639	$ 1,234,522,000