Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2014	Apr. 30, 2013
Basis of Presentation (Textual)
USF charges	$ 0.2	$ 0.2	$ 0.5	$ 0.7

Universal Service Fund Charges Billed To Customers Reported Gross

No definition available.

Name:	idt_UniversalServiceFundChargesBilledToCustomersReportedGross
Namespace Prefix:	idt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration