Consolidated Statements of Changes in Net Assets - USD ($) $ in Thousands		3 Months Ended						12 Months Ended
		Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Beginning balance			$ 1,341,569		$ 1,275,848		$ 1,161,315	$ 1,341,569	$ 1,275,848	$ 1,161,315
Beginning balance, Shares			81,389,287		75,771,542		67,684,209	81,389,287	75,771,542	67,684,209
Net investment income		$ 54,684	$ 42,937	$ 52,613	$ 35,712	$ 46,191	$ 32,310	$ 196,399	$ 166,327	$ 142,359
Net change in unrealized gains (losses) on investments and foreign currency translation								13,191	(74,969)	40,546
Net realized gain (loss) on investments and foreign currency transactions								12,433	16,695	28,875
Purchases of treasury stock								$ (6,200)	$ (6,168)
Purchases of treasury stock, Shares								0	368,206
Issuance of common stock, net of offering and underwriting costs								$ 89,204		85,904
Common stock issued in settlement of convertible notes									$ 77,642	42,273
Stock issued in connection with dividend reinvestment plan								$ 23,545	$ 30,516	36,351
Stock issued in connection with dividend reinvestment plan, Shares								1,265,212	1,625,826
Dividends declared from distributable earnings								$ (179,966)	$ (144,322)	(261,490)
Ending balance		$ 1,496,375		$ 1,341,569		$ 1,275,848		$ 1,496,375	$ 1,341,569	$ 1,275,848
Ending balance,Shares		87,829,499		81,389,287		75,771,542		87,829,499	81,389,287	75,771,542
Accounting Standards Update [Extensible Enumeration]										Cumulative Effect, Period of Adoption, Adjustment
Cumulative Effect, Period of Adoption, Adjustment
Beginning balance							(285)			$ (285)
Common Stock
Beginning balance			$ 821		$ 761		$ 680	$ 821	$ 761	$ 680
Beginning balance, Shares			81,389,287		75,771,542		67,684,209	81,389,287	75,771,542	67,684,209
Purchases of treasury stock, Shares									(368,206)
Issuance of common stock, net of offering and underwriting costs								$ 52		$ 41
Issuance of common stock, net of offering and underwriting costs, Shares								5,175,000		4,049,689
Common stock issued in settlement of convertible notes									$ 44	$ 24
Common stock issued in settlement of convertible notes, Shares									4,360,125	2,324,820
Stock issued in connection with dividend reinvestment plan								$ 12	$ 16	$ 16
Stock issued in connection with dividend reinvestment plan, Shares								1,265,212	1,625,826	1,712,824
Ending balance		$ 885		$ 821		$ 761		$ 885	$ 821	$ 761
Ending balance,Shares		87,829,499		81,389,287		75,771,542		87,829,499	81,389,287	75,771,542
Treasury Stock
Beginning balance			$ (10,459)		$ (4,291)		$ (4,291)	$ (10,459)	$ (4,291)	$ (4,291)
Beginning balance, Shares			664,250		296,044		296,044	664,250	296,044	296,044
Purchases of treasury stock									$ 6,168
Purchases of treasury stock, Shares									368,206
Ending balance		$ (10,459)		$ (10,459)		$ (4,291)		$ (10,459)	$ (10,459)	$ (4,291)
Ending balance,Shares		664,250		664,250		296,044		664,250	664,250	296,044
Paid in Capital in Excess of Par
Beginning balance			$ 1,294,751		$ 1,189,275		$ 1,025,676	$ 1,294,751	$ 1,189,275	$ 1,025,676
Issuance of common stock, net of offering and underwriting costs								89,152		85,863
Common stock issued in settlement of convertible notes									77,598	42,249
Stock issued in connection with dividend reinvestment plan								23,533	30,500	36,335
Tax reclassification of stockholders' equity in accordance with GAAP	[1]							(2,263)	(2,622)	(391)
Ending balance		$ 1,405,173		$ 1,294,751		$ 1,189,275		1,405,173	1,294,751	1,189,275
Paid in Capital in Excess of Par | Cumulative Effect, Period of Adoption, Adjustment
Beginning balance							(457)			(457)
Distributable Earnings
Beginning balance			$ 56,456		$ 90,103		139,250	56,456	90,103	139,250
Net investment income								196,399	166,327	142,359
Net change in unrealized gains (losses) on investments and foreign currency translation								13,191	(74,969)	40,546
Net realized gain (loss) on investments and foreign currency transactions								12,433	16,695	28,875
Dividends declared from distributable earnings								(179,966)	(144,322)	(261,490)
Tax reclassification of stockholders' equity in accordance with GAAP	[1]							2,263	2,622	391
Ending balance		$ 100,776		$ 56,456		$ 90,103		$ 100,776	$ 56,456	90,103
Distributable Earnings | Cumulative Effect, Period of Adoption, Adjustment
Beginning balance							$ 172			$ 172

[1] The Company's tax year end is currently March 31, however the Company intends to change its tax year end to December 31 during calendar year 2024.