Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2019	Apr. 30, 2018
Schedule of accumulated balances for each classification of other comprehensive income (loss)
Beginning balance			$ (4,972)
Other comprehensive income attributable to IDT Corporation	$ (10)	$ 204	474	$ 16
Ending balance	(4,465)		(4,465)
Unrealized Gain (Loss) on Available-for-Sale Securities [Member]
Schedule of accumulated balances for each classification of other comprehensive income (loss)
Beginning balance			(34)
Adjustment from the adoption of change in accounting for equity investments (see Note 8)			33
Adjusted balance, August 1, 2018			(1)
Other comprehensive income attributable to IDT Corporation			1
Ending balance
Foreign Currency Translation [Member]
Schedule of accumulated balances for each classification of other comprehensive income (loss)
Beginning balance			(4,938)
Adjustment from the adoption of change in accounting for equity investments (see Note 8)
Adjusted balance, August 1, 2018			(4,938)
Other comprehensive income attributable to IDT Corporation			473
Ending balance	(4,465)		(4,465)
Accumulated Other Comprehensive Loss [Member]
Schedule of accumulated balances for each classification of other comprehensive income (loss)
Beginning balance			(4,972)
Adjustment from the adoption of change in accounting for equity investments (see Note 8)			33
Adjusted balance, August 1, 2018			(4,939)
Other comprehensive income attributable to IDT Corporation			474
Ending balance	$ (4,465)		$ (4,465)