Equity - Summary of Changes in Components of Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2014	Jan. 31, 2013
Changes in the components of equity
Beginning Balance			$ 89,136
Dividends declared ($0.17 per share)			(3,917)
Restricted Class B common stock purchased from employees			(955)
Exercise of stock options			528
Stock issued for matching contributions to the 401(k) Plan			119
Purchase of stock of subsidiary			(1,133)
Adjustment to liabilities in connection with the Straight Path Spin-Off			(1,624)
Distributions to noncontrolling interests			(626)	(816)
Stock-based compensation	1,632	1,806	4,127	2,818
Comprehensive income:
Net income	2,535	2,953	6,058	6,567
Net income attributable to noncontrolling interests	(438)	(542)	(965)	(1,096)
Net income	2,973	3,495	7,023	7,663
Foreign currency translation adjustments	518	1,645	1,182	3,273
Comprehensive income	3,491	5,140	8,205	10,936
Comprehensive Income Net Of Tax	3,053	4,637	7,240	9,887
Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest	438	503	965	1,049
Ending Balance	93,860		93,860
Attributable to IDT Corporation [Member]
Changes in the components of equity
Beginning Balance			88,603
Dividends declared ($0.17 per share)			(3,917)
Restricted Class B common stock purchased from employees			(955)
Stock issued for matching contributions to the 401(k) Plan			525
Purchase of stock of subsidiary			(1,154)
Adjustment to liabilities in connection with the Straight Path Spin-Off			(1,624)
Distributions to noncontrolling interests
Stock-based compensation			4,105
Comprehensive income:
Net income			6,058
Foreign currency translation adjustments			1,182
Comprehensive income			7,240
Ending Balance	92,942		92,942
Noncontrolling Interests [Member]
Changes in the components of equity
Beginning Balance			533
Dividends declared ($0.17 per share)
Restricted Class B common stock purchased from employees
Stock issued for matching contributions to the 401(k) Plan			3
Purchase of stock of subsidiary			21
Adjustment to liabilities in connection with the Straight Path Spin-Off
Distributions to noncontrolling interests			(626)
Stock-based compensation			22
Comprehensive income:
Net income attributable to noncontrolling interests			(965)
Foreign currency translation adjustments
Comprehensive Income Net Of Tax			965
Ending Balance	$ 918		$ 918