Commitments and Contingencies - Restricted Cash and Cash Equivalents (Detail) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2012	Jul. 31, 2011
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-short-term	$ 12,636	$ 4,128
Restricted cash and cash equivalents-long-term	9,466	12,241
Total restricted cash and cash equivalents	22,102	16,369
Restricted Cash And Cash Equivalents-Short-Term [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-short-term	12,636	4,128
Restricted Cash And Cash Equivalents-Long-Term [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-long-term	9,466	12,241
IDT Financial Services Customer Deposits [Member] \| Restricted Cash And Cash Equivalents-Short-Term [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-short-term	11,206	1,248
IDT Financial Services Customer Deposits [Member] \| Restricted Cash And Cash Equivalents-Long-Term [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-long-term	6,703	8,703
Letter of Credit [Member] \| Restricted Cash And Cash Equivalents-Short-Term [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-short-term	1,430	2,880
Letter of Credit [Member] \| Restricted Cash And Cash Equivalents-Long-Term [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents-long-term	$ 2,763	$ 3,538

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element.

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The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against short-term borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. For a classified balance sheet represents the current portion only (the noncurrent portion has a separate concept); there is a separate and distinct element for unclassified presentations.

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