Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Schedule of accumulated balances for each classification of other comprehensive income (loss)
Beginning balance			$ (2,343)
Net other comprehensive (loss) income attributable to IDT Corporation	$ 204	$ 1,159	16	$ (1,307)
Ending balance	(4,597)		(4,597)
Unrealized Gain (Loss) on Available-for-Sale Securities [Member]
Schedule of accumulated balances for each classification of other comprehensive income (loss)
Beginning balance			2,134
Rafael Spin-Off			(1,991)
Other comprehensive (loss) income attributable to IDT Corporation before reclassifications			(138)
Less: reclassification for loss included in net loss			16
Net other comprehensive (loss) income attributable to IDT Corporation			(122)
Ending balance	21		21
Foreign Currency Translation [Member]
Schedule of accumulated balances for each classification of other comprehensive income (loss)
Beginning balance			(4,477)
Rafael Spin-Off			(279)
Other comprehensive (loss) income attributable to IDT Corporation before reclassifications			138
Less: reclassification for loss included in net loss
Net other comprehensive (loss) income attributable to IDT Corporation			138
Ending balance	(4,618)		(4,618)
Accumulated Other Comprehensive Loss [Member]
Schedule of accumulated balances for each classification of other comprehensive income (loss)
Beginning balance			(2,343)
Rafael Spin-Off			(2,270)
Other comprehensive (loss) income attributable to IDT Corporation before reclassifications
Less: reclassification for loss included in net loss			16
Net other comprehensive (loss) income attributable to IDT Corporation			16
Ending balance	$ (4,597)		$ (4,597)