RELATED PARTY TRANSACTIONS - Narrative (Details)				3 Months Ended					9 Months Ended		12 Months Ended
	Jan. 03, 2020	Mar. 18, 2019 USD ($)	Jan. 18, 2019	Sep. 30, 2021 USD ($) contract	Jun. 30, 2021 USD ($) contract	Mar. 31, 2021 USD ($) contract	Sep. 30, 2020 USD ($) contract	Mar. 31, 2020 USD ($) contract	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2019	Dec. 31, 2020 USD ($)
Related Party Transaction [Line Items]
Management fee percentage (as a percent)											1.50%
Quarterly management fee percentage (as a percent)											0.375%
Management fee expense				$ 807,967			$ 588,530		$ 2,122,199	$ 1,763,562
Management fee payable				811,000			588,000		811,000	588,000
Incentive fees				0			86,577		132,231	86,577
Incentive fees payable				132,231			86,577		132,231	86,577
Reimbursable expenses				511,117			441,349		1,320,170	1,249,123
Reimbursable expenses payable				$ 512,730			441,000		512,730	441,000
Percentage reduced of amount of waived exit fee (as a percent)				50.00%
Reimbursable expenses waived				$ 95,270			0		$ 271,229	73,549
Number of participation interests funded | contract					18
Hunt CRE 2017-FL1, Ltd.
Related Party Transaction [Line Items]
Funded participation interests												$ 5,600,000
Manager Equity Plan
Related Party Transaction [Line Items]
Maximum shares issued, percentage of issued and outstanding shares of common stock (as a percent)									3.00%
Manager Equity Plan | Restricted Stock Units (RSUs)
Related Party Transaction [Line Items]
Compensation expense									$ 10,867	17,343
Unrecognized compensation expense				$ 13,296			$ 8,302		$ 13,296	$ 8,302
Weighted average period for compensation expense not yet recognized									8 months 18 days
Hunt Investment Management, LLC
Related Party Transaction [Line Items]
Quarterly management fee percentage (as a percent)	0.375%
Quarterly incentive fee percentage (as a percent)	20.00%		20.00%
Hurdle rate percentage (as a percent)	8.00%		8.00%
Annual management fee percentage (as a percent)	1.50%
Hunt Investment Management, LLC | Support Agreement
Related Party Transaction [Line Items]
Maximum reduction of expense reimbursement per annum (percent)		25.00%
Maximum expense reimbursement reduction per annum		$ 568,000
Aggregate reduction of expense reimbursement		$ 1,960,000
Lument Structured Finance | Hunt CRE 2018-FL2, Ltd
Related Party Transaction [Line Items]
Number of loans purchased | contract						3
Unpaid principal balance of purchased loans						$ 34,900,000
Lument Structured Finance | Hunt CRE 2018-FL1, LTD.
Related Party Transaction [Line Items]
Number of loans purchased | contract					6
Unpaid principal balance of purchased loans					$ 67,800,000
Lument Structured Finance | LFT CRE 2021-FL1, Ltd.
Related Party Transaction [Line Items]
Number of loans purchased | contract				15	8
Unpaid principal balance of purchased loans				$ 309,100,000	$ 82,600,000
Lument Structured Finance | Hunt CRE 2017-FL1, Ltd.
Related Party Transaction [Line Items]
Number of loans purchased | contract							1	2
Unpaid principal balance of purchased loans							$ 9,500,000	$ 31,900,000
Lument Structured Finance | Lument Commercial Mortgage Trust
Related Party Transaction [Line Items]
Number of loans purchased | contract					2
Unpaid principal balance of purchased loans					$ 21,200,000
Funded participation interests					$ 14,500,000
OREC 2018-CRE1, Ltd. | LFT CRE 2021-FL1, Ltd.
Related Party Transaction [Line Items]
Number of loans purchased | contract					9
Unpaid principal balance of purchased loans					$ 112,500,000
Payment of premium on unpaid principal balance of purchased loans					$ 350,000
ORIX Real Estate Holdings, LLC | LFT CRE 2021-FL1, Ltd.
Related Party Transaction [Line Items]
Number of loans purchased | contract					8
Unpaid principal balance of purchased loans					$ 4,600,000
Payment of premium on unpaid principal balance of purchased loans					$ 20,000.00