Equity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2017	Apr. 30, 2016
Changes in the components of equity
Beginning Balance			$ 124,203
Dividends declared ($0.57 per share)			(13,155)
Sale of Class B common stock to Howard S. Jonas			10,000
Restricted Class B common stock purchased from employees			(1,838)
Exercise of stock options			835
Sale of interest and rights in Rafael Pharmaceuticals, Inc. to Howard S. Jonas			1,000
Issuance of member interests in CS Pharma Holdings, LLC			10,000
Distributions to noncontrolling interests			(1,139)
Stock-based compensation			2,793
Comprehensive income:
Net income	$ (4,452)	$ 4,701	19,099	13,941
Other comprehensive loss	1,159	1,962	(1,307)	(1,553)
Comprehensive income	(3,293)	$ 6,663	17,792	$ 12,388
Ending Balance	150,491		150,491
Attributable to IDT Corporation [Member]
Changes in the components of equity
Beginning Balance			123,797
Dividends declared ($0.57 per share)			(13,155)
Sale of Class B common stock to Howard S. Jonas			10,000
Restricted Class B common stock purchased from employees			(1,838)
Exercise of stock options			835
Sale of interest and rights in Rafael Pharmaceuticals, Inc. to Howard S. Jonas			(185)
Issuance of member interests in CS Pharma Holdings, LLC			1,850
Distributions to noncontrolling interests
Stock-based compensation			2,793
Comprehensive income:
Net income			18,018
Other comprehensive loss			(1,307)
Comprehensive income			16,711
Ending Balance	140,808		140,808
Noncontrolling Interests [Member]
Changes in the components of equity
Beginning Balance			406
Dividends declared ($0.57 per share)
Sale of Class B common stock to Howard S. Jonas
Restricted Class B common stock purchased from employees
Exercise of stock options
Sale of interest and rights in Rafael Pharmaceuticals, Inc. to Howard S. Jonas			1,185
Issuance of member interests in CS Pharma Holdings, LLC			8,150
Distributions to noncontrolling interests			(1,139)
Stock-based compensation
Comprehensive income:
Net income			1,081
Other comprehensive loss
Comprehensive income			1,081
Ending Balance	$ 9,683		$ 9,683