USE OF SPECIAL PURPOSE ENTITIES AND VARIABLE INTEREST ENTITIES - Summary of Loan and Borrowing Characteristics (Details)		9 Months Ended	12 Months Ended
		Sep. 30, 2021 USD ($) mortgage_loan contract insturment	Dec. 31, 2020 USD ($) insturment contract mortgage_loan
Variable Interest Entity [Line Items]
Collateralized loan obligations	[1]	$ 826,145,358	$ 463,060,090
Commercial real estate portfolio segment
Variable Interest Entity [Line Items]
Number of Loans | mortgage_loan		53	40
Carrying Value		$ 803,074,256	$ 547,345,334
LFT CRE 2021-FL1, Ltd.
Variable Interest Entity [Line Items]
Number of notes issued | insturment		1
Collateralized loan obligations		$ 826,145,358
LFT CRE 2021-FL1, Ltd. | London Interbank Offered Rate (LIBOR)
Variable Interest Entity [Line Items]
Weighted Average Yield (as a percentage)		3.46%
Interest fixed rate (as a percent)		1.43%
LFT CRE 2021-FL1, Ltd. | Commercial real estate portfolio segment
Variable Interest Entity [Line Items]
Number of Loans | contract		53
Hunt CRE 2017-FL1, Ltd. and Hunt CRE 2018-FL2, Ltd.
Variable Interest Entity [Line Items]
Number of notes issued | insturment			2
Collateralized loan obligations			$ 463,060,090
Hunt CRE 2017-FL1, Ltd. and Hunt CRE 2018-FL2, Ltd. | London Interbank Offered Rate (LIBOR)
Variable Interest Entity [Line Items]
Weighted Average Yield (as a percentage)			3.50%
Interest fixed rate (as a percent)			1.44%
Hunt CRE 2017-FL1, Ltd. and Hunt CRE 2018-FL2, Ltd. | Commercial real estate portfolio segment
Variable Interest Entity [Line Items]
Number of Loans | contract			40
Face Amount
Variable Interest Entity [Line Items]
Collateralized loan obligations			$ 465,316,126
Face Amount | LFT CRE 2021-FL1, Ltd.
Variable Interest Entity [Line Items]
Carrying Value		$ 803,043,750
Collateralized loan obligations		833,750,000
Face Amount | Hunt CRE 2017-FL1, Ltd. and Hunt CRE 2018-FL2, Ltd.
Variable Interest Entity [Line Items]
Carrying Value			531,363,401
Collateralized loan obligations			465,316,126
Carrying Value
Variable Interest Entity [Line Items]
Collateralized loan obligations			463,060,090
Carrying Value | LFT CRE 2021-FL1, Ltd.
Variable Interest Entity [Line Items]
Carrying Value		803,074,256
Collateralized loan obligations		826,145,358
Debt issuance costs		$ 7,604,638
Carrying Value | Hunt CRE 2017-FL1, Ltd. and Hunt CRE 2018-FL2, Ltd.
Variable Interest Entity [Line Items]
Carrying Value			531,363,401
Collateralized loan obligations			463,060,090
Carrying Value | Hunt CRE 2017-FL1, Ltd.
Variable Interest Entity [Line Items]
Debt discount			207,767
Carrying Value | Hunt CRE 2018-FL2, Ltd
Variable Interest Entity [Line Items]
Collateralized loan obligations			$ 2,048,269

[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.