v3.26.3
Prospect Capital InterNotes® - Schedule of Notes Outstanding (Details) - USD ($)
$ in Thousands
Sep. 30, 2026
Jun. 30, 2026
Sep. 30, 2025
Debt Instrument [Line Items]      
Principal Outstanding $ 1,537,158 $ 1,878,595  
Net Carrying Value 1,521,525 1,860,649  
Prospect Capital InterNotes®      
Debt Instrument [Line Items]      
Unamortized debt issuance (6,965) (7,399)  
Prospect Capital InterNotes® | Unsecured Debt      
Debt Instrument [Line Items]      
Principal Outstanding 598,228 614,879  
Unamortized debt issuance (6,965) (7,399)  
Net Carrying Value $ 591,263 $ 607,480  
Weighted Average Interest Rate 6.30%   7.42%
Prospect Capital InterNotes® | Unsecured Debt | Minimum      
Debt Instrument [Line Items]      
Interest Rate Range 6.00%   6.25%
Prospect Capital InterNotes® | Unsecured Debt | Maximum      
Debt Instrument [Line Items]      
Interest Rate Range 6.75%   8.00%
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2027 – September 15, 2029      
Debt Instrument [Line Items]      
Tenor at Origination (in years) 3 years 3 years  
Principal Outstanding $ 122,164 $ 121,738  
Weighted Average Interest Rate 6.81% 6.81%  
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2027 – September 15, 2029 | Minimum      
Debt Instrument [Line Items]      
Interest Rate Range 6.00% 6.00%  
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2027 – September 15, 2029 | Maximum      
Debt Instrument [Line Items]      
Interest Rate Range 7.50% 7.50%  
Prospect Capital InterNotes® | Unsecured Debt | October 15, 2026 – September 15, 2031      
Debt Instrument [Line Items]      
Tenor at Origination (in years) 5 years 5 years  
Principal Outstanding $ 150,214 $ 165,432  
Weighted Average Interest Rate 6.03% 5.70%  
Prospect Capital InterNotes® | Unsecured Debt | October 15, 2026 – September 15, 2031 | Minimum      
Debt Instrument [Line Items]      
Interest Rate Range 2.25% 2.25%  
Prospect Capital InterNotes® | Unsecured Debt | October 15, 2026 – September 15, 2031 | Maximum      
Debt Instrument [Line Items]      
Interest Rate Range 7.75% 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 $ 18,232  
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 – August 15, 2033      
Debt Instrument [Line Items]      
Tenor at Origination (in years) 7 years 7 years  
Principal Outstanding $ 41,454 $ 41,353  
Weighted Average Interest Rate 4.66% 4.65%  
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2028 – August 15, 2033 | Minimum      
Debt Instrument [Line Items]      
Interest Rate Range 2.75% 2.75%  
Prospect Capital InterNotes® | Unsecured Debt | January 15, 2028 – August 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 $ 3,090  
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 10 years  
Principal Outstanding $ 160,358 $ 160,770  
Weighted Average Interest Rate 5.91% 5.89%  
Prospect Capital InterNotes® | Unsecured Debt | August 15, 2029 – December 15, 2034 | Minimum      
Debt Instrument [Line Items]      
Interest Rate Range 3.15% 3.15%  
Prospect Capital InterNotes® | Unsecured Debt | August 15, 2029 – December 15, 2034 | Maximum      
Debt Instrument [Line Items]      
Interest Rate Range 8.00% 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 $ 11,899 $ 12,101  
Weighted Average Interest Rate 3.94% 3.94%  
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 $ 11,845 $ 12,340  
Weighted Average Interest Rate 3.85% 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 $ 2,839  
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 $ 7,168  
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 $ 65,101 $ 65,952  
Weighted Average Interest Rate 5.44% 5.42%  
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%