Document and Entity Information (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Jul. 31, 2013	Jan. 31, 2013	Oct. 05, 2013 Class B Common Stock [Member]	Oct. 05, 2013 Class A Common Stock [Member]
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Jul. 31, 2013
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	FY
Trading Symbol	IDT
Entity Registrant Name	IDT CORP
Entity Central Index Key	0001005731
Current Fiscal Year End Date	--07-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding			21,411,789	1,574,326
Entity Public Float		$ 183.9