Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 771
Sale of interest in Fabrix Systems Ltd.		$ 640
Ending balance	(3,744)	771
Unrealized gain (loss) on available-for-sale securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(575)	(8)
Other comprehensive income (loss) attributable to IDT Corporation before reclassification	1,126	(567)	(8)
Net other comprehensive income (loss) attributable to IDT Corporation	583
Ending balance	8	(575)	(8)
Unrealized gain (loss) on available-for-sale securities [Member] | Other income (expense), net [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Less: reclassification for gain included in net income	(543)
Foreign currency translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	1,346	3,676	2,341
Sale of interest in Fabrix Systems Ltd.		102
Zedge Spin-Off	1,029
Other comprehensive income (loss) attributable to IDT Corporation before reclassification	(6,127)	(2,432)	1,335
Net other comprehensive income (loss) attributable to IDT Corporation	(6,127)
Ending balance	(3,752)	1,346	3,676
Foreign currency translation [Member] | Other income (expense), net [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Less: reclassification for gain included in net income
Accumulated other comprehensive income (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	771	3,668	2,341
Zedge Spin-Off	1,029
Other comprehensive income (loss) attributable to IDT Corporation before reclassification	(5,001)	(2,999)	1,327
Net other comprehensive income (loss) attributable to IDT Corporation	(5,544)
Ending balance	(3,744)	$ 771	$ 3,668
Accumulated other comprehensive income (loss) [Member] | Other income (expense), net [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Less: reclassification for gain included in net income	$ (543)