Commitments and Contingencies - Restricted Cash and Cash Equivalents (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2014	Jul. 31, 2013
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-short-term	$ 57,606	$ 34,988
Restricted cash and cash equivalents-long-term	2,763	7,407
Total restricted cash and cash equivalents	60,369	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	732	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	55,505	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	1,369	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