Commitments and Contingencies - Restricted Cash and Cash Equivalents (Detail) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2013	Jul. 31, 2012
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-short-term	$ 34,988	$ 12,636
Restricted cash and cash equivalents-long-term	7,407	9,466
Total restricted cash and cash equivalents	42,395	22,102
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	3,189	1,430
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	31,076	11,154
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	723	52
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	2,768	2,763
Restricted Cash And Cash Equivalents-Long-Term [Member] | IDT Financial Services Customer Deposits [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-long-term	$ 4,639	$ 6,703