FINANCIAL HIGHLIGHTS (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares
Per Share Data:(1)
Net asset value at beginning of period	$ 14.02	$ 14.61	$ 14.03	$ 14.14	$ 14.09	$ 13.81	$ 13.69	$ 13.19	$ 13.94
Net investment income	1.92	1.46	1.01	1.13	1.23	1.42	1.21	1.39	1.33	$ 1.34
Change in unrealized appreciation (depreciation) on investments	0.13	(0.90)	(0.36)	0.44	(0.85)	(0.11)		1.49	(0.74)	(0.53)
Net realized (loss) gain	(1.38)	0.19	1.22	(0.52)	1.07	0.35	0.31	(1.05)	0.03	0.04
Loss on debt extinguishment			(0.03)
Provision for taxes on realized gains	0.14		(0.15)
(Provision) benefit for taxes on net unrealized (appreciation) depreciation on investments	(0.01)	(0.01)	0.03	(0.01)		(0.02)		0.03	(0.01)	(0.02)
Total from operations	0.80	0.74	1.72	1.04	1.45	1.64	1.52	1.86	0.61	0.83
Sales load	(0.04)				(0.06)		(0.09)			(0.01)
Offering costs	(0.01)	(0.03)			(0.03)		(0.02)
Net investment income	(1.59)	(1.11)	(1.09)	(1.15)	(0.54)	(1.03)	(1.20)	(1.36)	(1.33)	(1.31)
Net realized capital gains	(0.02)	(0.19)	(0.05)		(0.82)	(0.33)	(0.16)		(0.03)	(0.12)
Accretive effect of stock offerings (issuing shares above net asset value per share)	0.09				0.05
Other(6)	0.01						0.07			0.01
Net asset value at end of period	13.26	14.02	14.61	14.03	14.14	14.09	13.81	13.69	13.19	13.94
Per share market value at end of period	$ 12.85	$ 13.26	$ 13.02	$ 10.88	$ 14.23	$ 12.95	$ 13.14	$ 12.06	$ 9.64	$ 11.78
Total return based on market value(2)	8.72%	12.32%	30.78%	(13.73%)	21.97%	8.68%	20.29%	42.83%	(7.76%)	(13.09%)
Weighted Average Shares of Common Stock Outstanding Basic | shares	22,004,648	19,552,931	19,489,750	19,471,500	18,275,696	15,953,571	14,870,981	12,479,959	12,479,961	12,281,178
Weighted Average Shares of Common Stock Outstanding Diluted | shares	22,004,648	19,552,931	19,489,750	19,471,500	18,275,696	15,953,571	14,870,981	12,479,959	12,479,961	12,281,178
Ratio/Supplemental Data:(1)
Net assets at end of period | $	$ 319,939,788	$ 275,776,613	$ 285,111,233	$ 273,360,649	$ 270,571,173	$ 224,845,007	$ 220,247,242	$ 170,881,785	$ 164,651,104	$ 173,949,452
Weighted average net assets | $	$ 301,285,626	$ 281,745,332	$ 274,188,692	$ 253,034,571	$ 259,020,507	$ 223,750,302	$ 195,211,550	$ 165,189,142	$ 173,453,813	$ 176,458,141
Annualized ratio of gross operating expenses to net assets(5)	21.27	16.59	16.90	13.75	14.11	13.72	11.10	13.20	11.16	9.92
Annualized ratio of net operating expenses to net assets	21.16	16.59	16.90	13.75	14.11	13.72	11.10	13.20	10.78	9.12
Annualized ratio of interest expense and other fees to net assets	10.62	8.68	6.83	6.29	5.78	5.51	4.02	4.84	3.56	3.01
Annualized ratio of net investment income before fee waiver to net assets	13.91	8.68	6.83	6.29	5.78	10.09	9.21	10.71	9.11	8.40
Annualized ratio of net investment income to net assets(5)	14.01%	10.15%	7.21%	8.58%	8.64%	10.09%	9.21%	10.71%	9.49%	9.19%
Portfolio turnover(3)	15	15	39	21	23	32	48	16	29	19
2026 Notes payable | $	$ 98,996,412	$ 98,549,692	$ 100,000,000	$ 48,875,000	$ 48,875,000	$ 48,875,000	$ 48,875,000	$ 25,000,000	$ 25,000,000	$ 25,000,000
Credit Facility payable | $	160,085,705	199,200,425	177,340,000	174,000,000	161,550,000	99,550,000	40,750,000	116,000,000	109,500,000	106,500,000
SBA Debentures, net of prepaid loan fees | $	$ 325,000,000	$ 313,600,000	$ 250,000,000	$ 176,500,000	$ 161,000,000	$ 150,000,000	$ 90,000,000	$ 65,000,000	$ 65,000,000	$ 16,250,000
Asset coverage ratio(4)	2.23	1.92	2.03	2.23	2.29	2.51	3.46	2.21	2.22	2.32
Debt extinguishment costs | $			$ (539,250)				$ (416,725)
Debt extinguishment cost ratio			7.02%				4.24%
(Provision) benefit for taxes on net unrealized (appreciation) depreciation on investments | $	$ (126,957)	$ (213,214)	$ 510,868	$ (224,877)	$ (66,760)			$ 373,131	$ (93,601)	$ (288,122)
Benefit (provision) for taxes on net realized loss (gain) on investments | $	$ 2,987,847		$ (2,957,220)
Impact of tax provision benefit on net realized gain (loss) or unrealized (appreciation) depreciation to net assets	(0.04%)	(0.08%)	(0.89%)	(0.09%)	(0.03%)			(0.16%)	0.05%	0.17%
Deferred Offering Costs | $	$ 7,312	$ 1,100						$ 261,761