Consolidated Statements of Changes in Net Assets (Unaudited) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended								9 Months Ended
		Dec. 31, 2021	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022		Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021		Sep. 30, 2022	Sep. 30, 2021
Beginning balance			$ 1,241,959	$ 1,283,985	$ 1,275,848		$ 1,223,813	$ 1,185,332	$ 1,161,315		$ 1,275,848	$ 1,161,315
Net investment income			37,180	40,822	35,712		36,470	27,388	32,310		113,714	96,167
Net change in unrealized gain (losses) on investments and foreign currency translation			(5,134)	(54,751)	(8,495)		29,046	28,945	9,755		(68,379)	67,747
Net realized gains (losses) on investments and foreign currency transactions			2,385	404	13,668		$ (10,560)	2,021	14,587		16,456	$ 6,048
Issuance of common stock, net of offering and underwriting costs								(41)	85,945
Conversion of convertible notes			77,642
Conversion of convertible notes, Shares		2,324,820
Purchases of treasury stock			$ (3,000)								$ (3,000)
Purchases of treasury stock, Shares			180,542				0				180,542	0
Stock issued in connection with dividend reinvestment plan			$ 11,038	5,838	6,774		$ 4,396	14,298	4,709
Stock issued in connection with dividend reinvestment plan, Shares											1,219,840	1,115,079
Dividends declared from net investment income			(34,018)	(34,339)	(39,522)		(31,320)	(34,130)	(123,004)
Ending balance		$ 1,275,848	$ 1,328,052	1,241,959	1,283,985		$ 1,251,845	1,223,813	1,185,332		$ 1,328,052	$ 1,251,845
Ending balance,Shares			81,170,965				72,848,977				81,170,965	72,848,977
Accounting Standards Update [Extensible Enumeration]											us-gaap:AccountingStandardsUpdate202006Member
Cumulative Effect, Period of Adoption, Adjustment
Beginning balance	[1]								$ (285)			$ (285)
Accounting Standards Update [Extensible Enumeration]									us-gaap:AccountingStandardsUpdate202006Member
Common Stock
Beginning balance			$ 766	$ 764	$ 761		$ 729	$ 723	$ 680		$ 761	$ 680
Beginning balance, Shares			76,339,515	76,070,680	75,771,542		72,649,683	71,969,998	67,684,209		75,771,542	67,684,209
Issuance of common stock, net of offering and underwriting costs									$ 41
Issuance of common stock, net of offering and underwriting costs, Shares									4,049,689
Conversion of convertible notes			$ 44
Conversion of convertible notes, Shares			4,360,125
Purchases of treasury stock, Shares			(180,542)
Stock issued in connection with dividend reinvestment plan			$ 6	$ 2	$ 3		$ 2	$ 6	$ 2
Stock issued in connection with dividend reinvestment plan, Shares			651,867	268,835	299,138		199,294	679,685	236,100
Ending balance		$ 761	$ 816	$ 766	$ 764		$ 731	$ 729	$ 723		$ 816	$ 731
Ending balance,Shares		75,771,542	81,170,965	76,339,515	76,070,680		72,848,977	72,649,683	71,969,998		81,170,965	72,848,977
Treasury Stock
Beginning balance			$ (4,291)	$ (4,291)	$ (4,291)		$ (4,291)	$ (4,291)	$ (4,291)		$ (4,291)	$ (4,291)
Beginning balance, Shares			296,044	296,044	296,044		296,044	296,044	296,044		296,044	296,044
Purchases of treasury stock			$ (3,000)
Purchases of treasury stock, Shares			180,542
Ending balance		$ (4,291)	$ (7,291)	$ (4,291)	$ (4,291)		$ (4,291)	$ (4,291)	$ (4,291)		$ (7,291)	$ (4,291)
Ending balance,Shares		296,044	476,586	296,044	296,044		296,044	296,044	296,044		476,586	296,044
Paid in Capital in Excess of Par
Beginning balance			$ 1,201,531	$ 1,195,695	$ 1,189,275		$ 1,129,621	$ 1,115,370	$ 1,025,676		$ 1,189,275	$ 1,025,676
Issuance of common stock, net of offering and underwriting costs								(41)	85,904
Conversion of convertible notes			77,598
Stock issued in connection with dividend reinvestment plan			11,032	5,836	6,771		4,394	14,292	4,707
Tax reclassification of stockholders' equity in accordance with GAAP					(351)	[2]			(460)	[3]
Ending balance		$ 1,189,275	1,290,161	1,201,531	1,195,695		1,134,015	1,129,621	1,115,370		1,290,161	1,134,015
Paid in Capital in Excess of Par | Cumulative Effect, Period of Adoption, Adjustment
Beginning balance	[1]								(457)			(457)
Distributable Earnings
Beginning balance			43,953	91,817	90,103		97,754	73,530	139,250		90,103	139,250
Net investment income			37,180	40,822	35,712		36,470	27,388	32,310
Net change in unrealized gain (losses) on investments and foreign currency translation			(5,134)	(54,751)	(8,495)		29,046	28,945	9,755
Net realized gains (losses) on investments and foreign currency transactions			2,385	404	13,668		(10,560)	2,021	14,587
Dividends declared from net investment income			(34,018)	(34,339)	(39,522)		(31,320)	(34,130)	(123,004)
Tax reclassification of stockholders' equity in accordance with GAAP					351	[2]			460	[3]
Ending balance		$ 90,103	$ 44,366	$ 43,953	$ 91,817		$ 121,390	$ 97,754	73,530		$ 44,366	121,390
Distributable Earnings | Cumulative Effect, Period of Adoption, Adjustment
Beginning balance	[1]								$ 172			$ 172

[1] See Note 2 for further information related to the adoption of ASU 2020-06.

[2] The Company’s tax year end is March 31st.

[3] The Company’s tax year end is March 31st.