Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2020	Jan. 31, 2019
Schedule of accumulated balances for each classification of other comprehensive loss
Beginning balance			$ (4,858)
Other comprehensive loss attributable to IDT Corporation	$ (513)	$ (38)	(1,717)	$ 484
Ending balance	(6,575)		(6,575)
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			(1,717)
Ending balance	(6,575)		(6,575)
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			(1,717)
Ending balance	$ (6,575)		$ (6,575)