Financial Highlights (Details) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended											12 Months Ended
	Jul. 12, 2021	May 26, 2021	Aug. 03, 2020	Sep. 30, 2022	Jun. 30, 2022		Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021		Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2022		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Investment Company, Financial Highlights [Roll Forward]
Net asset value, beginning balance (in dollars per share)				$ 10.48				$ 10.12	$ 9.81					$ 8.18	$ 9.81		$ 8.18	$ 9.01	$ 9.35	$ 9.32
Net investment income (in dollars per share)				0.25	$ 0.23		$ 0.22	$ 0.22	0.21		$ 0.19	$ 0.19	$ 0.21	$ 0.15	0.88		0.75	0.72	0.85	0.79
Net realized and change in unrealized (losses) gains (in dollars per share)				(0.49)					0.33						0.61		1.77	(0.76)	(0.46)	0.04
Net increase from operations (in dollars per share)				(0.24)					0.54						1.49		2.51	(0.04)	0.39	0.83
Net increase from operations applicable to common stockholders (in dollars per share)				(0.27)					0.53						1.43		2.51	(0.04)	0.39	0.83
Return of Capital to common stockholders (in dollars per share)				0					0						(0.01)		(0.09)	(0.23)	0	0
Common stock transactions (in dollars per share)				(0.02)					(0.01)						(0.05)		(0.11)	(0.07)	(0.01)	(0.03)
Offering costs from issuance of preferred stock (in dollars per share)				0					(0.03)						(0.03)		(0.04)	0	0	0
Reclassification of preferred stock issuance costs (in dollars per share)															0.03		0	0	0	0
Net asset value, ending balance (in dollars per share)				10.01	10.48				10.12		9.81				10.48		9.81	8.18	9.01	9.35
Per share market value (in dollars per share)				$ 6.20	$ 6.99				$ 7.70		$ 8.39				$ 6.99		$ 8.39	$ 5.11	$ 6.53	$ 6.71
Total return based on market value				(9.06%)					(6.06%)						(8.59%)		85.53%	(11.35%)	8.23%	(7.42%)
Total return based on net asset value				(2.07%)					5.59%						17.21%		35.52%	2.84%	7.17%	12.39%
Shares outstanding at end of period (in shares)				396,179,053	393,164,437				389,504,713		388,419,573				393,164,437		388,419,573	373,538,499	367,131,025	364,409,938
Average weighted shares outstanding for the period (in shares)				394,337,440					388,886,142						390,571,648		382,705,106	368,094,299	365,984,541	361,456,075
Ratios/Supplemental Data
Net assets at end of period				$ 3,964,422	$ 4,119,123	[1]			$ 3,943,263	[1]	$ 3,945,517				$ 4,119,123	[1]	$ 3,945,517	$ 3,055,861	$ 3,306,275	$ 3,407,047
Portfolio turnover rate				1.98%					5.13%						15.92%		14.64%	16.46%	10.86%	30.70%
Ratio of operating expenses to average net assets applicable to common shares				10.23%					9.09%						9.00%		9.98%	11.37%	11.65%	11.08%
Ratio of net investment income to average net assets applicable to common shares				9.82%					8.40%						8.44%		8.24%	8.44%	9.32%	8.57%
5.50% Preferred Stock
Ratios/Supplemental Data
Dividend rate	5.50%	5.50%	5.50%	5.50%					5.50%
Preferred Stock
Investment Company, Financial Highlights [Roll Forward]
Distributions of net investment income (in dollars per share)				$ (0.03)					$ (0.01)						$ (0.06)		$ 0	$ 0	$ 0	$ 0
Ratios/Supplemental Data
Net assets at end of period									$ 0	[1]	$ 137,040						$ 137,040
Common Stock
Investment Company, Financial Highlights [Roll Forward]
Distributions of net investment income (in dollars per share)				$ (0.18)					$ (0.18)						$ (0.71)		$ (0.63)	$ (0.49)	$ (0.72)	$ (0.77)
Shares outstanding at end of period (in shares)				396,179,053	393,164,437	[1]			389,504,713	[1]	388,419,573				393,164,437	[1]	388,419,573
Ratios/Supplemental Data
Net assets at end of period				$ 396	$ 393	[1]			$ 390	[1]	$ 388				$ 393	[1]	$ 388

[1] Certain reclassifications have been made in the presentation of prior year amounts since initial disclosure in our Quarterly Report on Form 10-Q for the period ended September 30, 2021 to conform to the presentation in our Annual Report on Form 10-K for the year ended June 30, 2022. In addition, we have not yet finalized return of capital estimates for the current period. See Note 2 and Note 12 within the accompanying notes to consolidated financial statements for further discussion.