USE OF SPECIAL PURPOSE ENTITIES AND VARIABLE INTEREST ENTITIES - Summary of Loan and Borrowing Characteristics (Details)		9 Months Ended	12 Months Ended
		Sep. 30, 2023 USD ($) instrument contract mortgageLoan	Dec. 31, 2022 USD ($) contract mortgageLoan instrument
Variable Interest Entity [Line Items]
Collateralized loan obligations	[1]	$ 1,145,317,374	$ 829,310,498
One month LIBOR rate (as a percent)			4.18%
One month SOFR rate ( as a percent)		5.33%	4.19%
Weighted average LIBOR floor rate (as a percent)		0.41%	0.25%
SOFR spread rate (as a percent)		3.56%	3.41%
Basis spread on one-month LIBOR (percent)		1.99%	1.43%
One-Month LIBOR Rate
Variable Interest Entity [Line Items]
One month LIBOR rate (as a percent)			4.32%
Financing receivable, floating Rate (as a percent)		100.00%	80.40%
Secured​ Overnight ​Financing​ Rate
Variable Interest Entity [Line Items]
Financing receivable, floating Rate (as a percent)			19.60%
30-Day SOFR
Variable Interest Entity [Line Items]
30-day SOFR rate		0.0534
Commercial Real Estate Portfolio Segment
Variable Interest Entity [Line Items]
Collateral (loan investments) (Count) | mortgageLoan		87	71
Carrying Value		$ 1,355,547,986	$ 1,076,148,186
Financing receivable, floating Rate (as a percent)		100.00%	100.00%
2021-FL1 CLO
Variable Interest Entity [Line Items]
Financings provided, (Count) | instrument		2	1
Collateralized loan obligations		$ 1,145,317,374	$ 829,310,498
2021-FL1 CLO | One-Month LIBOR Rate
Variable Interest Entity [Line Items]
Weighted average yield (percent)		8.89%	7.60%
Weighted average yield (percent)		7.32%	5.75%
2021-FL1 CLO | Commercial Real Estate Portfolio Segment
Variable Interest Entity [Line Items]
Collateral (loan investments) (Count) | contract		86	64
Principal Value | 2021-FL1 CLO
Variable Interest Entity [Line Items]
Carrying Value		$ 1,350,912,660	$ 996,492,150
Collateralized loan obligations		1,151,450,000	833,750,000
Carrying Value | 2021-FL1 CLO
Variable Interest Entity [Line Items]
Carrying Value		1,339,006,196	996,511,403
Collateralized loan obligations		1,145,317,374	829,310,498
Debt issuance costs		2,548,732	4,439,502
Carrying Value | LMF 2023-1 Financing
Variable Interest Entity [Line Items]
Debt issuance costs		$ 3,583,894	$ 3,583,894

[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, 2023 and December 31, 2022, assets of consolidated VIEs totaled $1,384,961,307 and $1,005,507,371, respectively and the liabilities of consolidated VIEs totaled $1,149,063,668 and $831,575,144 respectively. See Note 4 for further discussion.