Document and Entity Information (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Jul. 31, 2014	Jan. 31, 2014	Oct. 06, 2014 Class B Common Stock [Member]	Oct. 06, 2014 Class A Common Stock [Member]
Document Information [Line Items]
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, 2014
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2014
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		$ 304.0
Entity Common Stock Shares Outstanding			21,663,733	1,574,326