v3.26.1
Cover - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2025
Mar. 23, 2026
Document Information [Line Items]    
Document Type 10-K  
Document Annual Report true  
Document Period End Date Dec. 31, 2025  
Current Fiscal Year End Date --12-31  
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 Well-known Seasoned Issuer No  
Entity Voluntary Filers No  
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  
ICFR Auditor Attestation Flag false  
Document Financial Statement Error Correction [Flag] false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   629,839,790
Documents Incorporated by Reference
Portions of the registrant’s definitive Proxy Statement for the 2026 Annual Meeting of Stockholders to be filed subsequently with the SEC are incorporated by reference into Part III of this Annual Report. Except with respect to information specifically incorporated by reference in this Annual Report, the Proxy Statement shall not be deemed to be filed as part hereof.
  
Entity Central Index Key 0002071778  
Amendment Flag false  
Document Fiscal Period Focus FY  
Document Fiscal Year Focus 2025  
Entity Public Float $ 0  
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