Equity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2016	Apr. 30, 2015
Changes in the components of equity [Abstract]
Beginning Balance			$ 134,940
Dividends declared ($0.56 per share)			(12,983)
Restricted Class B common stock purchased from employees			(134)
Repurchases of Class B common stock through repurchase program			(4,639)
Exercise of subsidiary stock options			9
Stock issued for matching contributions to the 401(k) Plan			1,411	$ 1,300
Distributions to noncontrolling interests			(1,545)
Stock-based compensation			2,317
Comprehensive income:
Net income	$ 4,701	$ 1,123	13,941	84,234
Other comprehensive income	1,962	1,062	(1,553)	(2,900)
Comprehensive income	6,663	$ 2,185	12,388	$ 81,334
Ending Balance	131,764		131,764
Attributable to IDT Corporation [Member]
Changes in the components of equity [Abstract]
Beginning Balance			133,831
Dividends declared ($0.56 per share)			(12,983)
Restricted Class B common stock purchased from employees			(134)
Repurchases of Class B common stock through repurchase program			$ (4,639)
Exercise of subsidiary stock options
Stock issued for matching contributions to the 401(k) Plan			$ 1,411
Distributions to noncontrolling interests
Stock-based compensation			$ 2,317
Comprehensive income:
Net income			12,496
Other comprehensive income			(1,553)
Comprehensive income			10,943
Ending Balance	130,746		130,746
Noncontrolling Interests [Member]
Changes in the components of equity [Abstract]
Beginning Balance			$ 1,109
Dividends declared ($0.56 per share)
Restricted Class B common stock purchased from employees
Repurchases of Class B common stock through repurchase program
Exercise of subsidiary stock options			$ 9
Stock issued for matching contributions to the 401(k) Plan
Distributions to noncontrolling interests			$ (1,545)
Stock-based compensation
Comprehensive income:
Net income			$ 1,445
Other comprehensive income
Comprehensive income			$ 1,445
Ending Balance	$ 1,018		$ 1,018