COMMERCIAL MORTGAGE LOANS HELD-FOR-INVESTMENT - Loan Portfolio Activity (Details) - USD ($)		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020
Loans Receivable Held-For-Investment, Net, Reconciliation To Cash Flow [Roll Forward]
Balance at December 31, 2020		$ 547,345,334
Purchases and fundings		647,459,391	$ 52,580,443
Proceeds from principal payments		(391,394,015)	(88,907,741)
Accretion of purchase discount		24,773	0
Amortization of Premiums on Held-for-investment Loans		(361,227)	$ 0
Balance at September 30, 2021	[1]	803,074,256
Commercial real estate portfolio segment
Loans Receivable Held-For-Investment, Net, Reconciliation To Cash Flow [Roll Forward]
Balance at December 31, 2020		547,345,334
Purchases and fundings		647,459,391
Proceeds from principal payments		(391,394,015)
Accretion of purchase discount		24,773
Amortization of Premiums on Held-for-investment Loans		(361,227)
Balance at September 30, 2021		$ 803,074,256

[1] Our consolidated balance sheets include assets and liabilities of consolidated variable interest entities ("VIEs") as the Company was the primary beneficiary of these VIEs. As of September 30, 2021 and December 31, 2020, assets of consolidated VIEs totaled $1,003,113,182 and $591,318,506, respectively and the liabilities of consolidated VIEs totaled $826,707,857 and $463,411,967 respectively. See Note 4 for further discussion.