Document and Entity Information - USD ($)	12 Months Ended
	Jul. 31, 2016	Oct. 10, 2016
Entity Registrant Name	IDT CORP
Entity Central Index Key	0001005731
Amendment Flag	false
Current Fiscal Year End Date	--07-31
Document Type	10-K
Document Period End Date	Jul. 31, 2016
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2016
Trading Symbol	IDT
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float	$ 254,500,000
Class A common stock
Entity Common Stock Shares Outstanding		1,574,326
Class B common stock
Entity Common Stock Shares Outstanding		21,473,945