Schedule IV - Mortgage Loans on Real Estate (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Unpaid Principal Balance	635,260,420
Carrying Amount of Loans	635,260,420	$ 555,172,891	$ 0
Multi-family | Illinois | Senior loan in excess of 3% | Borrower A
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Unpaid Principal Balance	35,625,000
Carrying Amount of Loans	35,625,000
Multi-family | Illinois | Senior loan in excess of 3% | Borrower G
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Unpaid Principal Balance	25,355,116
Carrying Amount of Loans	$ 25,355,116
Multi-family | Illinois | Senior loan in excess of 3% | London Interbank Offered Rate (LIBOR) | Borrower A
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.30%
Multi-family | Illinois | Senior loan in excess of 3% | London Interbank Offered Rate (LIBOR) | Borrower G
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.75%
Multi-family | Diversified | Senior loan in excess of 3% | Borrower B
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Unpaid Principal Balance	34,913,160
Carrying Amount of Loans	$ 34,913,160
Multi-family | Diversified | Senior loan in excess of 3% | London Interbank Offered Rate (LIBOR) | Borrower B
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.05%
Multi-family | Diversified | Senior loan less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Unpaid Principal Balance	314,964,735
Carrying Amount of Loans	$ 314,964,735
Multi-family | Diversified | Senior loan less than 3% | Minimum | London Interbank Offered Rate (LIBOR)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	2.80%
Multi-family | Diversified | Senior loan less than 3% | Maximum | London Interbank Offered Rate (LIBOR)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	5.95%
Multi-family | Texas | Senior loan in excess of 3% | Borrower C
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Unpaid Principal Balance	32,321,681
Carrying Amount of Loans	32,321,681
Multi-family | Texas | Senior loan in excess of 3% | Borrower H
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Unpaid Principal Balance	23,500,000
Carrying Amount of Loans	$ 23,500,000
Multi-family | Texas | Senior loan in excess of 3% | London Interbank Offered Rate (LIBOR) | Borrower C
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.65%
Multi-family | Texas | Senior loan in excess of 3% | London Interbank Offered Rate (LIBOR) | Borrower H
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.15%
Multi-family | Maryland | Senior loan in excess of 3% | Borrower D
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Unpaid Principal Balance	32,148,978
Carrying Amount of Loans	$ 32,148,978
Multi-family | Maryland | Senior loan in excess of 3% | London Interbank Offered Rate (LIBOR) | Borrower D
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.25%
Multi-family | Arizona | Senior loan in excess of 3% | Borrower E
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Unpaid Principal Balance	30,505,000
Carrying Amount of Loans	$ 30,505,000
Multi-family | Arizona | Senior loan in excess of 3% | London Interbank Offered Rate (LIBOR) | Borrower E
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.75%
Multi-family | Virginia | Senior loan in excess of 3% | Borrower F
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Unpaid Principal Balance	26,500,000
Carrying Amount of Loans	$ 26,500,000
Multi-family | Virginia | Senior loan in excess of 3% | London Interbank Offered Rate (LIBOR) | Borrower F
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	2.75%
Multi-family | Nebraska | Senior loan in excess of 3% | Borrower I
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Unpaid Principal Balance	20,853,067
Carrying Amount of Loans	$ 20,853,067
Multi-family | Nebraska | Senior loan in excess of 3% | London Interbank Offered Rate (LIBOR) | Borrower I
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.70%
Multi-family | Georgia | Senior loan in excess of 3% | Borrower K
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Unpaid Principal Balance	20,000,000
Carrying Amount of Loans	$ 20,000,000
Multi-family | Georgia | Senior loan in excess of 3% | London Interbank Offered Rate (LIBOR) | Borrower K
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	2.75%
Retail | Texas | Senior loan less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Unpaid Principal Balance	17,115,524
Carrying Amount of Loans	$ 17,115,524
Retail | Texas | Senior loan less than 3% | London Interbank Offered Rate (LIBOR)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.10%
Office | Illinois | Senior loan less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Unpaid Principal Balance	12,828,794
Carrying Amount of Loans	$ 12,828,794
Office | Illinois | Senior loan less than 3% | London Interbank Offered Rate (LIBOR)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.75%
Mixed-Use | District of Columbia | Senior loan less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Unpaid Principal Balance	4,404,365
Carrying Amount of Loans	$ 4,404,365
Mixed-Use | District of Columbia | Senior loan less than 3% | London Interbank Offered Rate (LIBOR)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.65%
Self-Storage | Virginia | Senior loan less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Unpaid Principal Balance	4,225,000
Carrying Amount of Loans	$ 4,225,000
Self-Storage | Virginia | Senior loan less than 3% | London Interbank Offered Rate (LIBOR)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.15%