NATURE OF OPERATIONS AND SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Details)	3 Months Ended		12 Months Ended										147 Months Ended
	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($) shares	Dec. 31, 2022 USD ($) shares	Dec. 31, 2021 USD ($) shares	Dec. 31, 2020 USD ($) shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($) shares	Dec. 31, 2012 USD ($) shares	Mar. 31, 2024 USD ($) shares
Nature of Operation And Significant Accounting Policies [Line Items]
Issuance of common stock, net of offering costs (shares) | shares			4,458,873	149,174	31,592	354,257	3,177,936	7,931	3,465,922	380,936	63,998	12,035,023	24,125,642
Gross Proceeds			$ 62,871,349	$ 2,070,935	$ 449,515	$ 5,023,843	$ 45,862,995	$ 93,737	$ 48,741,406	$ 5,485,780	$ 899,964	$ 180,522,093	$ 352,021,617
Proceeds for offering expenses and sales load fees													11,044,123
Offering expenses reimbursements													672,917
Proceeds from the issuance of common stock		$ 8,487,127											341,650,411
Credit Facility payable	$ 181,343,929		156,564,776										$ 181,343,929
Asset coverage ratio	214												214
Cash balance	$ 346,435												$ 346,435
Cash held in foreign currency	111,845												111,845
Cash held in foreign currency at acquisition cost	111,845
Cash exceeding the insured amount	96,435												96,435
Cash equivalents and carried at cost	48,415,286												48,415,286
SBA-guaranteed Debentures
Nature of Operation And Significant Accounting Policies [Line Items]
Estimated fair values	304,465,000												304,465,000
2026 Notes
Nature of Operation And Significant Accounting Policies [Line Items]
Estimated fair values	92,626,000												92,626,000
SBIC Subsidiary | SBA-guaranteed Debentures
Nature of Operation And Significant Accounting Policies [Line Items]
Maximum borrowing capacity	150,000,000												150,000,000
Regulatory capital	75,000,000		75,000,000										75,000,000
Credit Facility payable	150,000,000		150,000,000										150,000,000
SBIC II Subsidiary | SBA-guaranteed Debentures
Nature of Operation And Significant Accounting Policies [Line Items]
Maximum borrowing capacity	175,000,000												175,000,000
Regulatory capital	87,500,000		87,500,000										87,500,000
Credit Facility payable	$ 175,000,000		$ 175,000,000										$ 175,000,000