v3.26.1
Prospect Capital InterNotes® - Schedule of Notes Outstanding (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Jun. 30, 2025
Debt Instrument [Line Items]    
Principal Outstanding $ 1,878,595 $ 2,103,554
Net Carrying Value 1,860,649 2,088,311
Prospect Capital InterNotes®    
Debt Instrument [Line Items]    
Unamortized debt issuance (7,399) (8,687)
Prospect Capital InterNotes® | Unsecured Debt    
Debt Instrument [Line Items]    
Principal Outstanding 614,879 647,232
Unamortized debt issuance (7,399) (8,687)
Net Carrying Value $ 607,480 $ 638,545
Weighted Average Interest Rate 6.85% 7.15%
Prospect Capital InterNotes® | Unsecured Debt | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range 6.25% 6.50%
Prospect Capital InterNotes® | Unsecured Debt | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range 8.00% 8.00%
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2027 – July 15, 2029    
Debt Instrument [Line Items]    
Tenor at Origination (in years) 3 years  
Principal Outstanding $ 121,738  
Weighted Average Interest Rate 6.81%  
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2027 – July 15, 2029 | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range 6.00%  
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2027 – July 15, 2029 | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range 7.50%  
Prospect Capital InterNotes® | Unsecured Debt | July 15, 2026 – June 15, 2031    
Debt Instrument [Line Items]    
Tenor at Origination (in years) 5 years  
Principal Outstanding $ 165,432  
Weighted Average Interest Rate 5.70%  
Prospect Capital InterNotes® | Unsecured Debt | July 15, 2026 – June 15, 2031 | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range 2.25%  
Prospect Capital InterNotes® | Unsecured Debt | July 15, 2026 – June 15, 2031 | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range 7.75%  
Prospect Capital InterNotes® | Unsecured Debt | June 15, 2027 – November 15, 2029    
Debt Instrument [Line Items]    
Tenor at Origination (in years) 6 years 6 years
Principal Outstanding $ 18,232 $ 18,312
Weighted Average Interest Rate 3.56% 3.56%
Prospect Capital InterNotes® | Unsecured Debt | June 15, 2027 – November 15, 2029 | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range 3.00% 3.00%
Prospect Capital InterNotes® | Unsecured Debt | June 15, 2027 – November 15, 2029 | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range 6.25% 6.25%
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2028 – June 15, 2033    
Debt Instrument [Line Items]    
Tenor at Origination (in years) 7 years 7 years
Principal Outstanding $ 41,353 $ 35,069
Weighted Average Interest Rate 4.65% 4.14%
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2028 – June 15, 2033 | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range 2.75% 2.75%
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2028 – June 15, 2033 | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range 8.00% 8.00%
Prospect Capital InterNotes® | Unsecured Debt | June 15, 2029 – July 15, 2029    
Debt Instrument [Line Items]    
Tenor at Origination (in years) 8 years 8 years
Principal Outstanding $ 3,090 $ 3,190
Weighted Average Interest Rate 3.45% 3.45%
Prospect Capital InterNotes® | Unsecured Debt | June 15, 2029 – July 15, 2029 | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range 3.40% 3.40%
Prospect Capital InterNotes® | Unsecured Debt | June 15, 2029 – July 15, 2029 | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range 3.50% 3.50%
Prospect Capital InterNotes® | Unsecured Debt | August 15, 2029 – December 15, 2034    
Debt Instrument [Line Items]    
Tenor at Origination (in years) 10 years  
Principal Outstanding $ 160,770  
Weighted Average Interest Rate 5.89%  
Prospect Capital InterNotes® | Unsecured Debt | August 15, 2029 – December 15, 2034 | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range 3.15%  
Prospect Capital InterNotes® | Unsecured Debt | August 15, 2029 – December 15, 2034 | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range 8.00%  
Prospect Capital InterNotes® | Unsecured Debt | June 15, 2033 – July 15, 2033    
Debt Instrument [Line Items]    
Tenor at Origination (in years) 12 years 12 years
Principal Outstanding $ 12,101 $ 13,404
Weighted Average Interest Rate 3.94% 3.95%
Prospect Capital InterNotes® | Unsecured Debt | June 15, 2033 – July 15, 2033 | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range 3.70% 3.70%
Prospect Capital InterNotes® | Unsecured Debt | June 15, 2033 – July 15, 2033 | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range 4.00% 4.00%
Prospect Capital InterNotes® | Unsecured Debt | July 15, 2036 – February 15, 2037    
Debt Instrument [Line Items]    
Tenor at Origination (in years) 15 years 15 years
Principal Outstanding $ 12,340 $ 13,631
Weighted Average Interest Rate 3.84% 3.84%
Prospect Capital InterNotes® | Unsecured Debt | July 15, 2036 – February 15, 2037 | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range 3.50% 3.50%
Prospect Capital InterNotes® | Unsecured Debt | July 15, 2036 – February 15, 2037 | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range 4.50% 4.50%
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2031 – April 15, 2031    
Debt Instrument [Line Items]    
Tenor at Origination (in years) 18 years 18 years
Principal Outstanding $ 2,839 $ 2,949
Weighted Average Interest Rate 4.82% 4.82%
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2031 – April 15, 2031 | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range 4.50% 4.50%
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2031 – April 15, 2031 | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range 5.50% 5.50%
Prospect Capital InterNotes® | Unsecured Debt | November 15, 2032 – November 15, 2043    
Debt Instrument [Line Items]    
Tenor at Origination (in years) 20 years 20 years
Principal Outstanding $ 3,864 $ 3,864
Weighted Average Interest Rate 6.23% 6.23%
Prospect Capital InterNotes® | Unsecured Debt | November 15, 2032 – November 15, 2043 | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range 5.75% 5.75%
Prospect Capital InterNotes® | Unsecured Debt | November 15, 2032 – November 15, 2043 | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range 7.50% 7.50%
Prospect Capital InterNotes® | Unsecured Debt | November 15, 2038 – May 15, 2039    
Debt Instrument [Line Items]    
Tenor at Origination (in years) 25 years 25 years
Principal Outstanding $ 7,168 $ 7,287
Weighted Average Interest Rate 6.37% 6.37%
Prospect Capital InterNotes® | Unsecured Debt | November 15, 2038 – May 15, 2039 | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range 6.25% 6.25%
Prospect Capital InterNotes® | Unsecured Debt | November 15, 2038 – May 15, 2039 | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range 6.50% 6.50%
Prospect Capital InterNotes® | Unsecured Debt | November 15, 2042 – March 15, 2052    
Debt Instrument [Line Items]    
Tenor at Origination (in years) 30 years 30 years
Principal Outstanding $ 65,952 $ 70,776
Weighted Average Interest Rate 5.42% 5.38%
Prospect Capital InterNotes® | Unsecured Debt | November 15, 2042 – March 15, 2052 | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range 4.00% 4.00%
Prospect Capital InterNotes® | Unsecured Debt | November 15, 2042 – March 15, 2052 | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range 6.63% 6.63%
Prospect Capital InterNotes® | Unsecured Debt | October 15, 2025 – July 15, 2028    
Debt Instrument [Line Items]    
Tenor at Origination (in years)   3 years
Principal Outstanding   $ 123,367
Weighted Average Interest Rate   6.75%
Prospect Capital InterNotes® | Unsecured Debt | October 15, 2025 – July 15, 2028 | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range   5.00%
Prospect Capital InterNotes® | Unsecured Debt | October 15, 2025 – July 15, 2028 | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range   7.50%
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2026 – July 15, 2030    
Debt Instrument [Line Items]    
Tenor at Origination (in years)   5 years
Principal Outstanding   $ 192,095
Weighted Average Interest Rate   5.26%
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2026 – July 15, 2030 | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range   2.25%
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2026 – July 15, 2030 | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range   7.75%
Prospect Capital InterNotes® | Unsecured Debt | August 15, 2029 – December 15, 2034    
Debt Instrument [Line Items]    
Tenor at Origination (in years)   10 years
Principal Outstanding   $ 163,288
Weighted Average Interest Rate   5.86%
Prospect Capital InterNotes® | Unsecured Debt | August 15, 2029 – December 15, 2034 | Minimum    
Debt Instrument [Line Items]    
Interest Rate Range   3.15%
Prospect Capital InterNotes® | Unsecured Debt | August 15, 2029 – December 15, 2034 | Maximum    
Debt Instrument [Line Items]    
Interest Rate Range   8.00%