Equity (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2015	Oct. 31, 2014
Changes in the components of equity [Abstract]
Beginning Balance	$ 134,940
Dividends declared ($0.18 per share)	(4,199)
Restricted Class B common stock purchased from employees	(23)
Distributions to noncontrolling interests	(600)
Stock-based compensation	771
Comprehensive income:
Net income	4,575	$ 80,354
Other comprehensive income	639	(1,851)
Comprehensive income	5,214	$ 78,503
Ending Balance	136,103
Attributable to IDT Corporation [Member]
Changes in the components of equity [Abstract]
Beginning Balance	133,831
Dividends declared ($0.18 per share)	(4,199)
Restricted Class B common stock purchased from employees	$ (23)
Distributions to noncontrolling interests
Stock-based compensation	$ 771
Comprehensive income:
Net income	4,193
Other comprehensive income	639
Comprehensive income	4,832
Ending Balance	135,212
Noncontrolling Interests [Member]
Changes in the components of equity [Abstract]
Beginning Balance	$ 1,109
Dividends declared ($0.18 per share)
Restricted Class B common stock purchased from employees
Distributions to noncontrolling interests	$ (600)
Stock-based compensation
Comprehensive income:
Net income	$ 382
Other comprehensive income
Comprehensive income	$ 382
Ending Balance	$ 891