Commitments and Contingencies - Restricted Cash and Cash Equivalents (Detail) (USD $) In Thousands, unless otherwise specified	Oct. 31, 2013	Jul. 31, 2013
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-short-term	$ 40,258	$ 34,988
Restricted cash and cash equivalents-long-term	2,763	7,407
Total restricted cash and cash equivalents	43,021	42,395
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	939	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	38,708	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	611	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	2,768
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