v3.25.1
Cover - shares
3 Months Ended
Mar. 31, 2025
May 14, 2025
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2025  
Current Fiscal Year End Date --12-31  
Document Transition Report false  
Securities Act File Number 814-01253  
Entity Registrant Name Venture Lending & Leasing IX, Inc.  
Entity Incorporation, State or Country Code MD  
Entity Tax Identification Number 82-2040715  
Entity Address, Address Line One 104 La Mesa Drive  
Entity Address, Address Line Two Suite 102  
Entity Address, City or Town Portola Valley  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 94028  
City Area Code 650  
Local Phone Number 234-4300  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   100,000
Entity Central Index Key 0001717310  
Amendment Flag false  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q1