Cover - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2021	Oct. 12, 2021	Jan. 29, 2021
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Jul. 31, 2021
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2021
Current Fiscal Year End Date	--07-31
Entity File Number	1-16371
Entity Registrant Name	IDT Corporation
Entity Central Index Key	0001005731
Entity Tax Identification Number	22-3415036
Entity Incorporation, State or Country Code	DE
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 $0.1 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	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 292.2
ICFR Auditor Attestation Flag	true
Common Class B [Member]
Entity Common Stock, Shares Outstanding		24,187,563
Common Class A [Member]
Entity Common Stock, Shares Outstanding		1,574,326