v3.26.1
Cover - shares
6 Months Ended
Mar. 31, 2026
May 08, 2026
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2026  
Document Transition Report false  
Entity File Number 814-01505  
Entity Registrant Name Golub Capital Direct Lending Unlevered Corporation  
Entity Incorporation, State or Country Code MD  
Entity Tax Identification Number 88-1632039  
Entity Address, Address Line One 200 Park Avenue  
Entity Address, Address Line Two 25th Floor  
Entity Address, City or Town New York  
Entity Address, State or Province NY  
Entity Address, Postal Zip Code 10166  
City Area Code 212  
Local Phone Number 750-6060  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company true  
Entity Ex Transition Period true  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   26,772,467.472
Amendment Flag false  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q2  
Entity Central Index Key 0001901606  
Current Fiscal Year End Date --09-30