Document and Entity Information - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2019	Oct. 06, 2019	Jan. 31, 2019
Entity Registrant Name	IDT CORP
Entity Central Index Key	0001005731
Entity File Number	1-16371
Amendment Flag	false
Current Fiscal Year End Date	--07-31
Document Type	10-K
Document Period End Date	Jul. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Public Float			$ 148,200
Entity Interactive Data Current	Yes
Entity Incorporation State Country Code	DE
Class B common stock
Entity Common Stock Shares Outstanding		24,927,890
Class A common stock
Entity Common Stock Shares Outstanding		1,574,326