v3.25.1
Cover - shares
3 Months Ended
Mar. 31, 2025
Apr. 30, 2025
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2025  
Document Transition Report false  
Entity File Number 814-00757  
Entity Registrant Name FS KKR Capital Corp.  
Entity Incorporation, State or Country Code MD  
Entity Tax Identification Number 26-1630040  
Entity Address, Address Line One 201 Rouse Boulevard  
Entity Address, City or Town Philadelphia  
Entity Address, State or Province PA  
Entity Address, Postal Zip Code 19112  
City Area Code 215  
Local Phone Number 495-1150  
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  
Title of 12(b) Security Common stock, par value $0.001  
Trading Symbol FSK  
Security Exchange Name NYSE  
Entity Common Stock, Shares Outstanding   280,066,433
Entity Central Index Key 0001422183  
Amendment Flag false  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q1  
Current Fiscal Year End Date --12-31