Consolidated Statements of Changes in Net Assets - USD ($) $ in Thousands		3 Months Ended						12 Months Ended
		Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Beginning balance			$ 1,496,375		$ 1,341,569		$ 1,275,848	$ 1,496,375	$ 1,341,569	$ 1,275,848
Beginning balance, Shares			87,829,499		81,389,287		75,771,542	87,829,499	81,389,287	75,771,542
Net investment income		$ 57,585	$ 52,362	$ 54,684	$ 42,937	$ 52,613	$ 35,712	$ 220,017	$ 196,399	$ 166,327
Net change in unrealized gains (losses) on investments and foreign currency translation								(42,024)	13,191	(74,969)
Net realized gain (loss) on investments and foreign currency transactions								8,573	12,433	16,695
Issuance of common stock, net of offering and underwriting costs								$ 93,308	$ 89,204
Common stock issued in settlement of convertible notes										77,642
Purchases of treasury stock										(6,168)
Purchases of treasury stock, Shares								0	0
Stock issued in connection with dividend reinvestment plan								$ 24,723	$ 23,545	30,516
Stock issued in connection with dividend reinvestment plan, Shares								1,231,937	1,265,212
Dividends declared from distributable earnings								$ (193,443)	$ (179,966)	(144,322)
Ending balance		$ 1,607,529		$ 1,496,375		$ 1,341,569		$ 1,607,529	$ 1,496,375	$ 1,341,569
Ending balance,Shares		93,661,436		87,829,499		81,389,287		93,661,436	87,829,499	81,389,287
Common Stock
Beginning balance			$ 885		$ 821		$ 761	$ 885	$ 821	$ 761
Beginning balance, Shares			87,829,499		81,389,287		75,771,542	87,829,499	81,389,287	75,771,542
Issuance of common stock, net of offering and underwriting costs								$ 46	$ 52
Issuance of common stock, net of offering and underwriting costs, Shares								4,600,000	5,175,000
Common stock issued in settlement of convertible notes										$ 44
Common stock issued in settlement of convertible notes, Shares										4,360,125
Purchases of treasury stock, Shares										(368,206)
Stock issued in connection with dividend reinvestment plan								$ 12	$ 12	$ 16
Stock issued in connection with dividend reinvestment plan, Shares								1,231,937	1,265,212	1,625,826
Ending balance		$ 943		$ 885		$ 821		$ 943	$ 885	$ 821
Ending balance,Shares		93,661,436		87,829,499		81,389,287		93,661,436	87,829,499	81,389,287
Treasury Stock
Beginning balance			$ (10,459)		$ (10,459)		$ (4,291)	$ (10,459)	$ (10,459)	$ (4,291)
Beginning balance, Shares			664,250		664,250		296,044	664,250	664,250	296,044
Purchases of treasury stock										$ (6,168)
Purchases of treasury stock, Shares										368,206
Ending balance		$ (10,459)		$ (10,459)		$ (10,459)		$ (10,459)	$ (10,459)	$ (10,459)
Ending balance,Shares		664,250		664,250		664,250		664,250	664,250	664,250
Paid in Capital in Excess of Par
Beginning balance			$ 1,405,173		$ 1,294,751		$ 1,189,275	$ 1,405,173	$ 1,294,751	$ 1,189,275
Issuance of common stock, net of offering and underwriting costs								93,262	89,152
Common stock issued in settlement of convertible notes										77,598
Stock issued in connection with dividend reinvestment plan								24,711	23,533	30,500
Tax reclassification of stockholders' equity in accordance with GAAP	[1]							(3,809)	(2,263)	(2,622)
Ending balance		$ 1,519,337		$ 1,405,173		$ 1,294,751		1,519,337	1,405,173	1,294,751
Distributable Earnings
Beginning balance			$ 100,776		$ 56,456		$ 90,103	100,776	56,456	90,103
Net investment income								220,017	196,399	166,327
Net change in unrealized gains (losses) on investments and foreign currency translation								(42,024)	13,191	(74,969)
Net realized gain (loss) on investments and foreign currency transactions								8,573	12,433	16,695
Dividends declared from distributable earnings								(193,443)	(179,966)	(144,322)
Tax reclassification of stockholders' equity in accordance with GAAP	[1]							3,809	2,263	2,622
Ending balance		$ 97,708		$ 100,776		$ 56,456		$ 97,708	$ 100,776	$ 56,456

[1] The Company changed its tax year end from March 31st to December 31st.