Commitments and Contingencies - Restricted Cash and Cash Equivalents (Detail) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2014	Jul. 31, 2013
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-short-term	$ 65,706	$ 34,988
Restricted cash and cash equivalents-long-term	2,763	2,767
Total restricted cash and cash equivalents	68,469	37,755
Restricted Cash And Cash Equivalents-Short-Term [Member] | Letters of Credit Related [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-short-term	665	3,189
Restricted Cash And Cash Equivalents-Short-Term [Member] | IDT Financial Services Customer Deposits [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-short-term	64,415	31,076
Restricted Cash And Cash Equivalents-Short-Term [Member] | Other [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-short-term	626	723
Restricted Cash And Cash Equivalents-Long-Term [Member] | Letters of Credit Related [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-long-term	$ 2,763	$ 2,767