XML 8 R1.htm IDEA: XBRL DOCUMENT v3.25.1
Document and Entity Information - shares
 3 Months Ended
Mar. 31, 2025
May 02, 2025
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Fiscal Period Focus Q1  
Document Period End Date Mar. 31, 2025  
Entity Registrant Name Portman Ridge Finance Corporation  
Current Fiscal Year End Date --12-31  
Entity Central Index Key 0001372807  
Entity File Number 814-00735  
Entity Tax Identification Number 20-5951150  
Entity Current Reporting Status Yes  
Entity Address, Address Line One 650 Madison Avenue  
Entity Address, Address Line Two 3rd Floor  
Entity Address, City or Town New York  
Entity Address, State or Province NY  
Entity Address, Postal Zip Code 10022  
Entity Incorporation, State or Country Code DE  
Entity Filer Category Non-accelerated Filer  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Small Business false  
Trading Symbol PTMN  
City Area Code 212  
Local Phone Number 891-2880  
Title of 12(b) Security Common Stock, par value $0.01 per share  
Entity Interactive Data Current Yes  
Document Fiscal Year Focus 2025  
Security Exchange Name NASDAQ  
Entity Common Stock, Shares Outstanding   9,202,870
Document Quarterly Report true  
Document Transition Report false