Document and Entity Information - shares	9 Months Ended
	Apr. 30, 2018	Jun. 08, 2018
Entity Registrant Name	IDT CORP
Entity Central Index Key	0001005731
Amendment Flag	false
Trading Symbol	IDT
Current Fiscal Year End Date	--07-31
Document Type	10-Q
Document Period End Date	Apr. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Entity Filer Category	Accelerated Filer
Class A Common Stock
Entity Common Stock Shares Outstanding		1,574,326
Class B Common Stock
Entity Common Stock Shares Outstanding		23,278,153