CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023	Jun. 30, 2023
Operating Activities
Net increase (decrease) in net assets resulting from operations	$ 144,361	$ (89,014)	$ 233,278	$ (109,176)
Adjustments to reconcile net increase (decrease) in net assets resulting from operations to net cash used in operating activities:
Net realized losses on extinguishment of debt	68	58	212	138
Net realized losses on investments	69,763	32,213	277,129	39,092
Net change in unrealized (gains) losses on investments	(119,817)	158,923	(193,705)	378,096
Amortization of discounts (accretion of premiums), net			(4,155)	(4,215)
Accretion of original issue discount			2,156	5,255
Amortization of deferred financing costs			5,610	2,304
Payment-in-kind interest			(95,048)	(97,952)
Structuring fees			(4,816)	(8,705)
Change in operating assets and liabilities:
Payments for purchases of investments			(422,452)	(597,552)
Proceeds from sale of investments and collection of investment principal			298,586	302,099
Net Reductions to Subordinated Structured Notes and related investment cost			62,680	(1,130)
(Increase) decrease in due from broker			617	(400)
(Increase) decrease in interest receivable, net			(7,951)	(14,104)
(Increase) decrease in other receivables			(118)	(318)
(Increase) decrease in prepaid expenses			561	749
(Increase) decrease in due from Affiliate			(172)	(1)
Increase (decrease) in due to broker			8,810	0
Increase (decrease) in due to Prospect Capital Management			(5,043)	1,442
Increase (decrease) in accrued expenses			(1,639)	2,286
Increase (decrease) in interest payable			(2,057)	(6,680)
Increase (decrease) in other liabilities			(1,358)	(319)
Net Cash (Used in) Provided by Operating Activities			152,223	(101,244)
Financing Activities
Borrowings under Revolving Credit Facility (Note 4)			875,300	1,224,900
Principal payments under Revolving Credit Facility (Note 4)			(983,627)	(1,175,959)
Redemptions of Convertible Notes (Note 5)			0	(60,501)
Financing costs paid and deferred			(1,940)	(6,742)
Repurchase of Preferred Stock			(11,301)	0
Proceeds from issuance of preferred stock, net of underwriting costs			196,330	657,479
Offering costs from issuance of preferred stock			(3,521)	(9,764)
Dividends paid and distributions to stockholders			(269,238)	(222,123)
Net Cash Provided by (Used in) Financing Activities			(194,389)	130,972
Net Increase in Cash, Cash Equivalents and Restricted Cash			(42,166)	29,728
Cash, Cash Equivalents and Restricted Cash at beginning of period			95,646	35,364	$ 35,364
Cash, Cash Equivalents and Restricted Cash at End of Period	$ 53,480	$ 65,092	53,480	65,092	$ 95,646
Supplemental Disclosures
Cash paid for interest			114,769	108,291
Non-Cash Financing Activities
Value of shares issued through reinvestment of dividends			30,698	41,387
Affiliated Entity
Change in operating assets and liabilities:
Increase (decrease) in due to Affiliate			(161)	0
Related Party
Change in operating assets and liabilities:
Increase (decrease) in due to Affiliate			1,259	7,847
Preferred Stock to Common Stock
Non-Cash Financing Activities
Conversion of stock			40,952	12,994
Convertible Notes to Common Stock
Non-Cash Financing Activities
Conversion of stock			0	3,000
Public Notes
Financing Activities
Redemptions of unsecured debt			(81,240)	(284,218)
Prospect Capital InterNotes®
Financing Activities
Redemptions of unsecured debt			(9,317)	(5,433)
Issuances of Prospect Capital InterNotes® (Note 7)			$ 94,165	$ 13,333