v3.26.1
Document and Entity Information - USD ($)
 12 Months Ended
Jan. 31, 2026
Mar. 20, 2026
Jul. 31, 2025
Document And Entity Information      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Jan. 31, 2026    
Document Transition Report false    
Entity File Number 001-31756    
Entity Registrant Name ARGAN INC    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 13-1947195    
Entity Address, Address Line One 4075 Wilson Boulevard, Suite 440    
Entity Address, City or Town Arlington    
Entity Address, State or Province VA    
Entity Address, Postal Zip Code 22203    
City Area Code 301    
Local Phone Number 315-0027    
Title of 12(b) Security Common Stock, $0.15 par value    
Trading Symbol AGX    
Security Exchange Name NYSE    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Icfr Auditor Attestation Flag true    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 2,828,180,674
Entity Common Stock, Shares Outstanding   13,945,962  
Documents Incorporated by Reference

Portions of the Registrant’s Proxy Statement for the 2026 Annual Meeting of Stockholders are incorporated by reference in Part III of this form 10-K.

    
Auditor Firm ID 248    
Auditor Location Arlington, Virginia    
Auditor Name GRANT THORNTON LLP    
Entity Central Index Key 0000100591    
Current Fiscal Year End Date --01-31    
Document Fiscal Year Focus 2026    
Document Fiscal Period Focus FY    
Amendment Flag false