USE OF SPECIAL PURPOSE ENTITIES AND VARIABLE INTEREST ENTITIES - Summary of Loan and Borrowing Characteristics (Details)		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 31, 2024 mortgageLoan	Sep. 30, 2024 USD ($) instrument mortgageLoan contract	Dec. 31, 2023 USD ($) contract mortgageLoan instrument
Variable Interest Entity [Line Items]
Collateralized loan obligations and secured financings	[1]		$ 955,094,679	$ 1,146,210,752
One month SOFR rate ( as a percent)			5.16%	5.33%
Weighted average LIBOR floor rate (as a percent)			0.56%	0.38%
SOFR spread rate (as a percent)			3.58%	3.54%
Basis spread on one-month LIBOR (percent)			2.13%	1.99%
30-Day SOFR
Variable Interest Entity [Line Items]
30-day SOFR rate			0.0510	0.0536
Commercial Real Estate Portfolio Segment
Variable Interest Entity [Line Items]
Collateral (loan investments) (Count) | mortgageLoan		88	75	88
Carrying Value			$ 1,191,183,049	$ 1,389,940,203
Net of purchase discounts			$ 4,344,687	$ 7,000,863
2021-FL1 CLO and LMF 2023-1
Variable Interest Entity [Line Items]
Financings provided, (Count) | instrument			2	2
Collateralized loan obligations and secured financings			$ 955,094,679	$ 1,146,210,752
2021-FL1 CLO and LMF 2023-1 | Secured Overnight Financing Rate (SOFR)
Variable Interest Entity [Line Items]
Weighted average yield (percent)			8.74%	8.91%
Weighted average yield (percent)			7.23%	7.35%
2021-FL1 CLO and LMF 2023-1 | Commercial Real Estate Portfolio Segment
Variable Interest Entity [Line Items]
Collateral (loan investments) (Count) | contract			74	87
Principal Value | 2021-FL1 CLO and LMF 2023-1
Variable Interest Entity [Line Items]
Carrying Value			$ 1,175,548,857	$ 1,388,495,984
Collateralized loan obligations and secured financings			957,673,227	1,151,450,000
Principal Value | LFT CRE 2021-FL1, Ltd.
Variable Interest Entity [Line Items]
Net of purchase discounts			4,468,136	7,159,664
Carrying Value | 2021-FL1 CLO and LMF 2023-1
Variable Interest Entity [Line Items]
Carrying Value			1,161,565,228	1,375,277,312
Collateralized loan obligations and secured financings			955,094,679	1,146,210,752
Carrying Value | 2021-FL1 CLO
Variable Interest Entity [Line Items]
Debt issuance costs			13,851	1,911,547
Carrying Value | LMF 2023-1 Financing
Variable Interest Entity [Line Items]
Debt issuance costs			$ 2,564,697	$ 3,327,701

[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, 2024 and December 31, 2023, assets of consolidated VIEs totaled $1,187,880,140 and $1,384,136,334, respectively and the liabilities of consolidated VIEs totaled $958,170,808 and $1,150,207,290 respectively. See Note 4 for further discussion.