CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Jun. 30, 2023
Operating Activities
Net increase (decrease) in net assets resulting from operations	$ (27,744)	$ 72,277	$ 88,917	$ (20,162)
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	53	52	144	80
Net realized losses on investments	(123)	(16,298)	207,366	6,879
Net change in unrealized (gains) losses on investments	124,741	50,673	(73,888)	219,173
Amortization of discounts (accretion of premiums), net			(2,713)	(2,877)
Accretion of original issue discount			1,439	3,482
Amortization of deferred financing costs			3,720	1,539
Payment-in-kind interest			(62,358)	(51,026)
Structuring fees			(2,355)	(8,705)
Change in operating assets and liabilities:
Payments for purchases of investments			(238,088)	(552,780)
Proceeds from sale of investments and collection of investment principal			224,909	220,316
Net Reductions to Subordinated Structured Notes and related investment cost			40,212	1,194
Decrease in due from broker			475	0
(Increase) in interest receivable, net			(9,893)	(20,784)
(Increase) in other receivables			(3,546)	(229)
Decrease in prepaid expenses			378	665
(Increase) in due from affiliate			(16)	0
(Decrease) in due to broker			(94)	0
(Decrease) increase in due to Prospect Capital Management			(4,238)	3,293
(Decrease) increase in accrued expenses			(1,053)	2,101
Increase (decrease) in interest payable			95	(283)
(Decrease) in other liabilities			(932)	(782)
Net Cash (Used in) Provided by Operating Activities			174,487	(197,422)
Financing Activities
Borrowings under Revolving Credit Facility (Note 4)			501,300	628,400
Principal payments under Revolving Credit Facility (Note 4)			(651,954)	(713,559)
Redemptions of Convertible Notes (Note 5)			0	(60,501)
Financing costs paid and deferred			(1,088)	(5,858)
Repurchase of Preferred Stock			(11,301)	0
Proceeds from issuance of preferred stock, net of underwriting costs			133,281	531,664
Offering costs from issuance of preferred stock			(2,637)	(7,864)
Dividends paid and distributions to stockholders			(173,347)	(140,516)
Net Cash Provided by (Used in) Financing Activities			(172,844)	232,144
Net Increase in Cash, Cash Equivalents and Restricted Cash			1,643	34,722
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	$ 97,289	$ 70,086	97,289	70,086	$ 95,646
Supplemental Disclosures
Cash paid for interest			75,383	66,915
Non-Cash Financing Activities
Value of shares issued through reinvestment of dividends			20,136	31,208
Affiliated Entity
Change in operating assets and liabilities:
(Decrease) in due to affiliates			(161)	0
Related Party
Change in operating assets and liabilities:
(Decrease) in due to affiliates			6,167	1,484
Preferred Stock to Common Stock
Non-Cash Financing Activities
Conversion of stock			32,177	6,324
Convertible Notes to Common Stock
Non-Cash Financing Activities
Conversion of stock			0	3,000
Public Notes
Financing Activities
Redemptions of unsecured debt			0	(2,103)
Prospect Capital InterNotes®
Financing Activities
Redemptions of unsecured debt			(5,690)	(2,995)
Issuances of Prospect Capital InterNotes® (Note 7)			$ 38,592	$ 5,476