Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands	Total	Noncontrolling Interests	IDT Corp Additional Paid-In Capital	IDT Corp Treasury Stock	IDT Corp Accumulated Other Comprehensive Income	IDT Corp Accumulated Deficit	IDT Corp Class A Common Stock	IDT Corp Class B Common Stock
Beginning Balance at Jul. 31, 2014	$ 101,164	$ 925	$ 392,858	$ (99,841)	$ 3,668	$ (196,725)	$ 33	$ 246
Beginning Balance, Shares at Jul. 31, 2014							3,272	24,587
Dividends declared	(47,594)					(47,594)
Restricted Class B common stock purchased from employees	(2,777)			(2,777)
Repurchases of Class B common stock through repurchase program	(425)			(425)
Exercise of stock options	3,424		3,422					$ 2
Exercise of stock options, Shares								245
Stock-based compensation	5,666	62	5,604
Restricted stock issued to employees and directors			(4)					$ 4
Restricted stock issued to employees and directors, Shares								373
Stock issued for matching contributions to the 401(k) Plan	1,267		1,266					$ 1
Stock issued for matching contributions to the 401(k) Plan, Shares								71
Purchase of Class B common stock from Howard S. Jonas	(7,500)			(7,500)
Distributions to noncontrolling interests	(2,050)	(2,050)
Sale of interest in Fabrix Systems Ltd.	640	538			102
Other	9	9
Other comprehensive loss	(2,999)				(2,999)
Net income for the year	86,115	1,625				84,490
Ending Balance at Jul. 31, 2015	134,940	1,109	403,146	(110,543)	771	(159,829)	$ 33	$ 253
Ending Balance, Shares at Jul. 31, 2015							3,272	25,276
Dividends declared	(17,358)					(17,358)
Restricted Class B common stock purchased from employees	(134)			(134)
Repurchases of Class B common stock through repurchase program	(4,639)			(4,639)
Exercise of subsidiary stock options	9	9
Stock-based compensation	2,680		2,680
Restricted stock issued to employees and directors
Restricted stock issued to employees and directors, Shares								12
Stock issued for matching contributions to the 401(k) Plan	1,411		1,410					$ 1
Stock issued for matching contributions to the 401(k) Plan, Shares								95
Sale of Zedge equity prior to the spin-off	374		374
Distributions to noncontrolling interests	(1,834)	(1,834)
Zedge Spin-Off	(11,062)	(722)	(11,369)		1,029
Other	2		2
Other comprehensive loss	(5,544)				(5,544)
Net income for the year	25,358	1,844				23,514
Ending Balance at Jul. 31, 2016	124,203	406	396,243	(115,316)	(3,744)	(153,673)	$ 33	$ 254
Ending Balance, Shares at Jul. 31, 2016							3,272	25,383
Dividends declared	(17,874)					(17,874)
Restricted Class B common stock purchased from employees	(1,838)			(1,838)
Exercise of stock options	836		835					$ 1
Exercise of stock options, Shares								73
Stock-based compensation	3,740		3,739					$ 1
Stock-based compensation, Shares								105
Sale of Class B common stock to Howard S. Jonas	24,930		(8,920)	33,850
Sale of interest and rights in Rafael Pharmaceuticals, Inc. to Howard S. Jonas (see Note 2)	1,000	1,185	(185)
Issuance of member interests in CS Pharma Holdings, LLC (see Note 2)	10,000	7,250	2,750
Distributions to noncontrolling interests	(1,482)	(1,482)
Other comprehensive loss	1,401				1,401
Net income for the year	9,641	1,464				8,177
Ending Balance at Jul. 31, 2017	$ 154,557	$ 8,823	$ 394,462	$ (83,304)	$ (2,343)	$ (163,370)	$ 33	$ 256
Ending Balance, Shares at Jul. 31, 2017							3,272	25,561