v3.25.4
N-2 - $ / shares
 2 Months Ended 3 Months Ended
Mar. 11, 2026
Mar. 11, 2026
Dec. 31, 2025
Sep. 30, 2025
Jun. 30, 2025
Mar. 31, 2025
Dec. 31, 2024
Sep. 30, 2024
Jun. 30, 2024
Mar. 31, 2024
Dec. 31, 2023
Sep. 30, 2023
Cover [Abstract]                        
Entity Central Index Key 0001287032                      
Amendment Flag false                      
Document Type DEF 14A                      
Entity Registrant Name Prospect Capital Corporation                      
General Description of Registrant [Abstract]                        
Share Price [Table Text Block]
 NAV PerStock PricePremium
(Discount)
 Common Share(1)High(2)Low(2)High(3)Low(3)
Year Ended June 30, 2024
First quarter$9.25 $6.65 $5.94 (28.1)%(35.8)%
Second quarter8.92 6.18 5.08 (30.7)%(43.0)%
Third quarter8.99 6.24 5.33 (30.6)%(40.7)%
Fourth quarter8.74 5.69 6.085.21 (34.9)%(40.4)%
Year Ended June 30, 2025
First quarter$8.10 $5.60 $4.75 (30.9)%(41.4)%
Second quarter7.84 5.34 4.16 (31.9)%(46.9)%
Third quarter7.25 4.45 4.10 (38.6)%(43.4)%
Fourth quarter 6.56 4.06 3.14 (38.1)%(52.1)%
Twelve Months Ending June 30, 2026
First quarter$6.45 $3.47 $2.59 (46.2)%(59.8)%
Second quarter6.21 2.88 2.45 (53.6)%(60.5)%
Third quarter (through March 11, 2026)
(4)3.05 2.61 (4)(4)
(1)    NAV per common share is determined as of the last day in the relevant quarter and therefore may not reflect the NAV per common share on the date of the high or low sales price. The NAVs shown are based on outstanding common shares at the end of each period.
(2)    The High/Low stock price is calculated as of the closing price on a given day in the applicable quarter.
(3)    Calculated as the respective high or low closing sales price less NAV per common share, divided by NAV per common share (in each case as of the applicable quarter end).
(4)     NAV has not yet been finally determined for any day after December 31, 2025. Our most recently estimated NAV per common share is $6.21 on December 31, 2025. NAV per common share as of March 31, 2026 may be higher or lower than $6.21 based on potential changes in valuations, issuances of securities, dividends paid and earnings for the quarters then ended.
                      
Lowest Price or Bid   $ 2.61 $ 2.45 $ 2.59 $ 3.14 $ 4.10 $ 4.16 $ 4.75 $ 5.21 $ 5.33 $ 5.08 $ 5.94
Highest Price or Bid   $ 3.05 $ 2.88 $ 3.47 $ 4.06 $ 4.45 $ 5.34 $ 5.60 $ 5.69 $ 6.24 $ 6.18 $ 6.65
Highest Price or Bid, Premium (Discount) to NAV [Percent]     (53.60%) (46.20%) (38.10%) (38.60%) (31.90%) (30.90%) (34.90%) (30.60%) (30.70%) (28.10%)
Lowest Price or Bid, Premium (Discount) to NAV [Percent]     (60.50%) (59.80%) (52.10%) (43.40%) (46.90%) (41.40%) (40.40%) (40.70%) (43.00%) (35.80%)