v3.26.3
Document And Entity Information - USD ($)
 12 Months Ended
Jul. 31, 2026
Sep. 21, 2026
Jan. 31, 2026
Document Information [Line Items]      
Entity Central Index Key 0001005731    
Entity Registrant Name IDT CORP    
Amendment Flag false    
Current Fiscal Year End Date --07-31    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2026    
Document Type 10-K    
Document Annual Report true    
Document Period End Date Jul. 31, 2026    
Document Transition Report false    
Entity File Number 1-16371    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 22-3415036    
Entity Address, Address Line One 520 Broad Street    
Entity Address, City or Town Newark    
Entity Address, State or Province NJ    
Entity Address, Postal Zip Code 07102    
City Area Code 973    
Local Phone Number 438-1000    
Title of 12(b) Security Class B common stock, par value $0.01 per share    
Trading Symbol IDT    
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     $ 915,300,000
Auditor Firm ID 248    
Auditor Name GRANT THORNTON LLP    
Auditor Location New York, New York    
Common Class A [Member]      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   1,574,326  
Common Class B [Member]      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   23,264,360