Accumulated Other Comprehensive Income (Loss) - Schedule of Accumulated Balances for Each Classification of Other Comprehensive Income (Loss) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 202	$ 3,027	$ (1,017)
Genie Spin-Off		(438)
Other comprehensive income attributable to IDT Corporation	2,139	(2,387)	4,044
Ending balance	2,341	202	3,027
Unrealized Gain (Loss) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(4)	(131)
Genie Spin-Off
Other comprehensive income attributable to IDT Corporation		4	127
Ending balance			(4)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	202	3,031	(886)
Genie Spin-Off		(438)
Other comprehensive income attributable to IDT Corporation	2,139	(2,391)	3,917
Ending balance	$ 2,341	$ 202	$ 3,031