Debt - Narratives - Purchase agreement, Revolving credit facility (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 20, 2019 USD ($)	Dec. 12, 2018 USD ($)
Repurchase Agreements
Payment of financing costs	$ 84,175	$ 226,738
Document Period End Date	Mar. 31, 2020
Repayment of borrowings under repurchase agreements	$ 3,395,740	0
Proceeds from borrowings under repurchase agreement	14,807,834	45,347,521
Unarmortized Finance Cost	1,058,106			$ (1,400,000)
Proceeds from lines of credit	$ 35,000,000	$ 0
Revolving Credit Facility
Line of Credit Facility, Expiration Date	Jun. 20, 2020
Obligation under participation agreement	$ 67,670,405			103,186,327
Revolving Credit Facility
Revolving Credit Facility
Line of Credit Facility, Expiration Date	Jun. 20, 2020
Revolving Credit Facility | Floor rate
Revolving Credit Facility
Debt Instrument, Basis Spread on Variable Rate	6.00%
Revolving Credit Facility | LIBOR
Revolving Credit Facility
Debt Instrument, Basis Spread on Variable Rate	4.00%
Revolving Credit Facility | Prime Rate
Revolving Credit Facility
Debt Instrument, Basis Spread on Variable Rate	1.00%
Minimum | Revolving Credit Facility
Revolving Credit Facility
Line of Credit Facility, Periodic Payment, Principal	$ 1,000,000
Maximum | Revolving Credit Facility
Revolving Credit Facility
Line of Credit Facility, Remaining Borrowing Capacity	25,000,000.0
Master Repurchase Agreement
Repurchase Agreements
Payment of financing costs	2,800,000.0
Deferred Costs	$ 1,200,000.0
Maximum Liability Under Repurchase Agreement Percent	0.5
Debt Instrument, Increase, Accrued Interest	$ 0
Financing Receivable, Unamortized Loan Fee (Cost)				$ 1,500,000.0
Master Repurchase Agreement | Minimum
Repurchase Agreements
EBITDA To Interest Expense Ratio	1.50
Master Repurchase Agreement | Maximum
Repurchase Agreements
Banking Regulation, Tangible Capital Ratio, Actual	3.00
Israel Discount Bank of New York | Revolving Credit Facility
Repurchase Agreements
Minimum Net Worth Required for Compliance	$ 200,000,000.0
Ratio of Indebtedness to Net Capital	1.75
Israel Discount Bank of New York | Minimum | Revolving Credit Facility
Repurchase Agreements
EBITDA To Interest Expense Ratio	1.00
Israel Discount Bank of New York | Terra LOC Portfolio I, LLC | Revolving Credit Facility
Repurchase Agreements
Minimum Net Worth Required for Compliance	$ 100,000,000.0
Revolving Credit Facility
Line of Credit Facility, Maximum Borrowing Capacity					$ 35,000,000.0
Line of Credit Facility, Fair Value of Amount Outstanding	35,000,000.0
Goldman Sachs Bank USA | Terra Mortgage Capital LLC | Master Repurchase Agreement
Revolving Credit Facility
Line of Credit Facility, Maximum Borrowing Capacity						$ 150,000,000
Forecast | Master Repurchase Agreement | Minimum
Repurchase Agreements
Debt Instrument, Increase, Accrued Interest			$ 4,200,000
Multifamily
Revolving Credit Facility
Obligation under participation agreement	$ 44,500,000.0