Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2019	Oct. 31, 2018
Schedule of accumulated balances for each classification of other comprehensive loss
Beginning balance	$ (4,858)
Other comprehensive loss attributable to IDT Corporation	(1,204)	$ 522
Ending balance	(6,062)
Unrealized Gain (Loss) on Available-for-Sale Securities [Member]
Schedule of accumulated balances for each classification of other comprehensive loss
Beginning balance
Other comprehensive loss attributable to IDT Corporation
Ending balance
Foreign Currency Translation [Member]
Schedule of accumulated balances for each classification of other comprehensive loss
Beginning balance	(4,858)
Other comprehensive loss attributable to IDT Corporation	(1,204)
Ending balance	(6,062)
Accumulated Other Comprehensive Loss [Member]
Schedule of accumulated balances for each classification of other comprehensive loss
Beginning balance	(4,858)
Other comprehensive loss attributable to IDT Corporation	(1,204)
Ending balance	$ (6,062)