v3.26.3
Cover - shares
 3 Months Ended
Sep. 30, 2026
Nov. 03, 2026
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2026  
Document Transition Report false  
Entity File Number 814-00659  
Entity Registrant Name PROSPECT CAPITAL CORP  
Entity Incorporation, State or Country Code MD  
Entity Tax Identification Number 43-2048643  
Entity Address, Address Line One 10 East 40th Street  
Entity Address, City or Town New York  
Entity Address, State or Province NY  
Entity Address, Postal Zip Code 10016  
City Area Code 212  
Local Phone Number 448-0702  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   556,989,222
Entity Central Index Key 0001287032  
Current Fiscal Year End Date (here only for the Qs) --06-30  
Document Fiscal Year Focus 2027  
Document Fiscal Period Focus Q1  
Amendment Flag false  
Common Stock    
Document Information [Line Items]    
Title of 12(b) Security Common Stock, $0.001 par value  
Trading Symbol PSEC  
Security Exchange Name NASDAQ  
5.35% Preferred Stock    
Document Information [Line Items]    
Title of 12(b) Security 5.35% Series A Fixed Rate Cumulative Perpetual Preferred Stock, par value $0.001  
Trading Symbol PSEC PRA  
Security Exchange Name NYSE