Consolidated Statements of Changes in Net Assets - USD ($)		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Beginning balance		$ 318,522,353	$ 349,651,973	$ 315,010,277	$ 435,608,981
Accounting Standards Update [Extensible Enumeration]		ASU 2020-06
Issuance of common stock from the conversion of the 2022 Convertible Notes			30,000
Repurchase of common stock, value			(4,884,316)	(2,192,527)
Net investment income	[1]	$ 36,565,372	29,371,122	19,877,942
Net realized and unrealized gain (loss)		(10,329,102)	(25,884,146)	46,610,286
Dividends to common stockholders, excluding tax return of capital	[2]	(29,028,764)	(27,571,457)	(22,084,873)
Tax return of capital			(1,741,425)	(7,569,132)
Tax reclassification of stockholders' equity in accordance with generally accepted accounting principles		0	0	0
Ending balance		315,729,859	$ 318,522,353	$ 349,651,973	$ 315,010,277
Cumulative Effect of Adjustment
Beginning balance	[3]	$ (449,398)
Accounting Standards Update [Extensible Enumeration]		ASU 2020-06	ASU 2020-06	ASU 2020-06	ASU 2020-06
Ending balance	[3]		$ (449,398)
Common Stock
Beginning balance		$ 84,482	$ 84,478	$ 84,478
Beginning balance, Shares		72,571,907	73,876,987	74,466,665
Issuance of common stock from the conversion of the 2022 Convertible Notes			$ 4
Issuance of common stock from the conversion of the 2022 Convertible Notes, Shares			3,546
Repurchase of common stock, value			$ 0	$ 0
Repurchase of common stock, Shares			(1,308,626)	(589,678)
Net investment income		$ 0	$ 0	$ 0
Net realized and unrealized gain (loss)		0	0	0
Dividends to common stockholders, excluding tax return of capital	[2]	0	0	0
Tax return of capital			0	0
Tax reclassification of stockholders' equity in accordance with generally accepted accounting principles		0	0	0
Ending balance		$ 84,482	$ 84,482	$ 84,478	$ 84,478
Ending balance, Shares		72,571,907	72,571,907	73,876,987	74,466,665
Common Stock | Cumulative Effect of Adjustment
Beginning balance	[3]	$ 0
Accounting Standards Update [Extensible Enumeration]			ASU 2020-06
Ending balance	[3]		$ 0
Paid in Capital in Excess of Par
Beginning balance		850,199,351	852,360,178	$ 858,079,713
Issuance of common stock from the conversion of the 2022 Convertible Notes			29,996
Repurchase of common stock, value			0	0
Net investment income		0	0	0
Net realized and unrealized gain (loss)		0	0	0
Dividends to common stockholders, excluding tax return of capital	[2]	0	0	0
Tax return of capital			(1,741,425)	(7,569,132)
Tax reclassification of stockholders' equity in accordance with generally accepted accounting principles		(874,693)	3,888,233	1,849,597
Ending balance		849,324,658	$ 850,199,351	852,360,178	$ 858,079,713
Paid in Capital in Excess of Par | Cumulative Effect of Adjustment
Beginning balance	[3]	(4,337,631)
Accounting Standards Update [Extensible Enumeration]			ASU 2020-06
Ending balance	[3]		$ (4,337,631)
Distributable Earnings (Loss)
Beginning balance		(458,387,778)	(434,303,297)	(476,857,055)
Issuance of common stock from the conversion of the 2022 Convertible Notes			0
Repurchase of common stock, value			0	0
Net investment income		36,565,372	29,371,122	19,877,942
Net realized and unrealized gain (loss)		(10,329,102)	(25,884,146)	46,610,286
Dividends to common stockholders, excluding tax return of capital	[2]	(29,028,764)	(27,571,457)	(22,084,873)
Tax return of capital			0	0
Tax reclassification of stockholders' equity in accordance with generally accepted accounting principles		874,693	(3,888,233)	(1,849,597)
Ending balance		(460,305,579)	$ (458,387,778)	(434,303,297)	(476,857,055)
Distributable Earnings (Loss) | Cumulative Effect of Adjustment
Beginning balance	[3]	3,888,233
Accounting Standards Update [Extensible Enumeration]			ASU 2020-06
Ending balance	[3]		$ 3,888,233
Treasury Stock at Cost
Beginning balance		(73,373,702)	(68,489,386)	(66,296,859)
Issuance of common stock from the conversion of the 2022 Convertible Notes			0
Repurchase of common stock, value			(4,884,316)	(2,192,527)
Net investment income		0	0	0
Net realized and unrealized gain (loss)		0	0	0
Dividends to common stockholders, excluding tax return of capital	[2]	0	0	0
Tax return of capital			0	0
Tax reclassification of stockholders' equity in accordance with generally accepted accounting principles		0	0	0
Ending balance		(73,373,702)	$ (73,373,702)	$ (68,489,386)	$ (66,296,859)
Treasury Stock at Cost | Cumulative Effect of Adjustment
Beginning balance	[3]	$ 0
Accounting Standards Update [Extensible Enumeration]			ASU 2020-06
Ending balance	[3]		$ 0

[1] Net investment income and per share amounts displayed above are net of the accrual (reversal) for incentive fees on capital gains which is reflected on a hypothetical liquidation basis in accordance with GAAP for the years ended December 31, 2022 and 2021 (see Note 3).

[2] Dividends for annual periods are determined in accordance with federal income tax regulations and there may be differences between book and tax amounts (see Note 2).

[3] See Notes 2 and 4 for further information related to the adoption of ASU 2020-06.