Equity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015
Changes in the components of equity [Abstract]
Beginning Balance			$ 134,940
Dividends declared ($0.37 per share)			(8,626)
Restricted Class B common stock purchased from employees			(134)
Repurchases of Class B common stock through repurchase program			(4,639)
Distributions to noncontrolling interests			(1,220)
Stock-based compensation			1,644
Comprehensive income:
Net income	$ 4,663	$ 2,757	9,240	$ 83,111
Other comprehensive income	(4,154)	(2,111)	(3,515)	(3,962)
Comprehensive income	509	$ 646	5,725	$ 79,149
Ending Balance	127,690		127,690
Attributable to IDT Corporation [Member]
Changes in the components of equity [Abstract]
Beginning Balance			133,831
Dividends declared ($0.37 per share)			(8,626)
Restricted Class B common stock purchased from employees			(134)
Repurchases of Class B common stock through repurchase program			$ (4,639)
Distributions to noncontrolling interests
Stock-based compensation			$ 1,644
Comprehensive income:
Net income			8,259
Other comprehensive income			(3,515)
Comprehensive income			4,744
Ending Balance	126,820		126,820
Noncontrolling Interests [Member]
Changes in the components of equity [Abstract]
Beginning Balance			$ 1,109
Dividends declared ($0.37 per share)
Restricted Class B common stock purchased from employees
Repurchases of Class B common stock through repurchase program
Distributions to noncontrolling interests			$ (1,220)
Stock-based compensation
Comprehensive income:
Net income			$ 981
Other comprehensive income
Comprehensive income			$ 981
Ending Balance	$ 870		$ 870