Investment in Real Estate-Related Loan - Floating Rate CMBS (Details)	6 Months Ended
	Jun. 30, 2020 USD ($)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Face Amount, Securities, Mortgage Backed	$ 33,075,000
Cost of Investment, Securities, Mortgage Backed	29,413,318
Unrealized Gain (Loss), Securities, Mortgage Backed	521,235
Carrying Amount, Securities, Mortgage Backed	29,934,553
BX 2020 BXLP G [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Face Amount, Securities, Mortgage Backed	10,827,000
Cost of Investment, Securities, Mortgage Backed	10,827,000
Unrealized Gain (Loss), Securities, Mortgage Backed	(487,215)
Carrying Amount, Securities, Mortgage Backed	10,339,785
CGDB 2019 MOB F [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Face Amount, Securities, Mortgage Backed	4,000,000
Cost of Investment, Securities, Mortgage Backed	4,005,000
Unrealized Gain (Loss), Securities, Mortgage Backed	(264,600)
Carrying Amount, Securities, Mortgage Backed	3,740,400
BXMT 2020 FL 2 [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Face Amount, Securities, Mortgage Backed	4,000,000
Cost of Investment, Securities, Mortgage Backed	4,000,000
Unrealized Gain (Loss), Securities, Mortgage Backed	(359,168)
Carrying Amount, Securities, Mortgage Backed	3,640,832
BX 2019 IMC G [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Face Amount, Securities, Mortgage Backed	3,700,000
Cost of Investment, Securities, Mortgage Backed	2,493,923
Unrealized Gain (Loss), Securities, Mortgage Backed	493,841
Carrying Amount, Securities, Mortgage Backed	2,987,764
BHMS 2018 ATLS D [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Face Amount, Securities, Mortgage Backed	1,998,000
Cost of Investment, Securities, Mortgage Backed	1,399,098
Unrealized Gain (Loss), Securities, Mortgage Backed	347,526
Carrying Amount, Securities, Mortgage Backed	1,746,624
BHMS 2018 ATLS E [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Face Amount, Securities, Mortgage Backed	1,550,000
Cost of Investment, Securities, Mortgage Backed	999,750
Unrealized Gain (Loss), Securities, Mortgage Backed	314,259
Carrying Amount, Securities, Mortgage Backed	1,314,009
BX 2020 VIVA D [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Face Amount, Securities, Mortgage Backed	4,680,982
Cost of Investment, Securities, Mortgage Backed	3,901,172
Unrealized Gain (Loss), Securities, Mortgage Backed	288,602
Carrying Amount, Securities, Mortgage Backed	4,189,774
BX 2020 VIVA E [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Face Amount, Securities, Mortgage Backed	2,319,018
Cost of Investment, Securities, Mortgage Backed	1,787,375
Unrealized Gain (Loss), Securities, Mortgage Backed	187,990
Carrying Amount, Securities, Mortgage Backed	$ 1,975,365
London Interbank Offered Rate (LIBOR) [Member] | BX 2020 BXLP G [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgage Backed Securities, Basis Spread On Variable Rate	2.50%
London Interbank Offered Rate (LIBOR) [Member] | CGDB 2019 MOB F [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgage Backed Securities, Basis Spread On Variable Rate	2.55%
London Interbank Offered Rate (LIBOR) [Member] | BXMT 2020 FL 2 [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgage Backed Securities, Basis Spread On Variable Rate	1.95%
London Interbank Offered Rate (LIBOR) [Member] | BX 2019 IMC G [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgage Backed Securities, Basis Spread On Variable Rate	3.60%
London Interbank Offered Rate (LIBOR) [Member] | BHMS 2018 ATLS D [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgage Backed Securities, Basis Spread On Variable Rate	2.25%
London Interbank Offered Rate (LIBOR) [Member] | BHMS 2018 ATLS E [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgage Backed Securities, Basis Spread On Variable Rate	3.00%
London Interbank Offered Rate (LIBOR) [Member] | BX 2020 VIVA D [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgage Backed Securities, Basis Spread On Variable Rate	3.67%
London Interbank Offered Rate (LIBOR) [Member] | BX 2020 VIVA E [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgage Backed Securities, Basis Spread On Variable Rate	3.67%