Commitments and Contingencies - Restricted Cash and Cash Equivalents (Detail) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2014	Jul. 31, 2013
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-short-term	$ 53,298	$ 34,988
Restricted cash and cash equivalents-long-term	2,763	2,767
Total restricted cash and cash equivalents	56,061	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	734	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	50,452	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	2,112	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