Document and Entity Information	9 Months Ended
	Apr. 30, 2015	Jun. 03, 2015
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-Q
Document Period End Date	Apr. 30, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q3
Entity Filer Category	Accelerated Filer
Class A common stock [Member]
Document Information [Line Items]
Entity Common Stock Shares Outstanding		1,574,326
Class B common stock [Member]
Document Information [Line Items]
Entity Common Stock Shares Outstanding		22,253,363