v3.26.1
Cover - shares
 3 Months Ended
Mar. 31, 2026
May 11, 2026
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2026  
Document Transition Report false  
Entity File Number 001-42888  
Registrant Name Fermi Inc.  
Entity Incorporation, State or Country Code TX  
Entity Tax Identification Number 33-3560468  
Entity Address, Address Line One 620 S. Taylor St.  
Entity Address, Address Line Two Suite 301  
Entity Address, City or Town Amarillo  
Entity Address, State or Province TX  
Entity Address, Postal Zip Code 79101  
City Area Code (214)  
Local Phone Number 894-7855  
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   637,574,239
Entity Central Index Key 0002071778  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Document Fiscal Period Focus Q1  
Document Fiscal Year Focus 2026  
Common Stock, $0.001 par value at Nasdaq Stock Market LLC    
Document Information [Line Items]    
Title of 12(b) Security Common Stock, $0.001 par value  
Trading Symbol FRMI  
Security Exchange Name NASDAQ  
Common Stock, $0.001 par value at London Stock Exchange    
Document Information [Line Items]    
Title of 12(b) Security Common Stock, $0.001 par value  
Trading Symbol FRMI