Consolidated Statements of Comprehensive (Loss) Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Consolidated Statements of Comprehensive Income [Abstract]
Net (loss) income	$ (3,230)	$ (4,452)	$ (3,336)	$ 19,099
Other comprehensive income (loss):
Change in unrealized gain on available-for-sale securities	28	102	(122)	39
Foreign currency translation adjustments	176	1,057	138	(1,346)
Other comprehensive income (loss)	204	1,159	16	(1,307)
Comprehensive (loss) income	(3,026)	(3,293)	(3,320)	17,792
Comprehensive income attributable to noncontrolling interests	(228)	(323)	(698)	(1,081)
Comprehensive (loss) income attributable to IDT Corporation	$ (3,254)	$ (3,616)	$ (4,018)	$ 16,711