Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Consolidated Statements of Income [Abstract]
REVENUES	$ 1,501,729	$ 1,496,261	$ 1,596,777
COSTS AND EXPENSES:
Direct cost of revenues (exclusive of depreciation and amortization)	1,275,708	1,246,594	1,328,363
Selling, general and administrative (i)	188,293	204,655	222,239
Depreciation and amortization	21,704	20,535	18,418
Research and development			1,656
Severance		6,510	8,363
TOTAL COSTS AND EXPENSES	1,485,705	1,478,294	1,579,039
Other (see Note 12)	(10,412)	(326)	(1,552)
(Adjustment to) gain on sale of member interest in Visa Europe Ltd.	(63)	7,476
Gain on sale of interest in Fabrix Systems, Ltd.		1,086	76,864
Income from operations	5,549	26,203	93,050
Interest income (expense), net	1,254	1,216	(159)
Other income (expense), net	817	2,049	(688)
Income before income taxes	7,620	29,468	92,203
Benefit from (provision for) income taxes	2,021	(4,110)	(6,088)
NET INCOME	9,641	25,358	86,115
Net income attributable to noncontrolling interests	(1,464)	(1,844)	(1,625)
NET INCOME ATTRIBUTABLE TO IDT CORPORATION	$ 8,177	$ 23,514	$ 84,490
Earnings per share attributable to IDT Corporation common stockholders:
Basic	$ 0.35	$ 1.03	$ 3.69
Diluted	$ 0.35	$ 1.03	$ 3.63
Weighted-average number of shares used in calculation of earnings per share:
Basic	23,182	22,765	22,903
Diluted	23,309	22,815	23,247
(i) Stock-based compensation included in selling, general and administrative expenses	$ 3,740	$ 2,680	$ 5,185