Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Consolidated Statements of Operations [Abstract]
Revenues		$ 395,883	$ 367,556	$ 789,438	$ 736,707
Costs and expenses:
Direct cost of revenues (exclusive of depreciation and amortization)		337,229	310,913	673,738	623,941
Selling, general and administrative	[1]	52,358	47,325	102,429	92,763
Depreciation and amortization		5,735	5,301	11,408	10,601
Severance		195		635
Total costs and expenses		395,517	363,539	788,210	727,305
Other operating expense		(846)	(889)	(1,625)	(1,088)
(Loss) income from operations		(480)	3,128	(397)	8,314
Interest income, net		286	309	648	609
Other income (expense), net		370	(419)	(456)	1,974
Income (loss) before income taxes		176	3,018	(205)	10,897
Benefit from (provision for) income taxes		1,514	(1,761)	99	12,655
Net income (loss)		1,690	1,257	(106)	23,552
Net income attributable to noncontrolling interests		(174)	(382)	(470)	(758)
Net income (loss) attributable to IDT Corporation		$ 1,516	$ 875	$ (576)	$ 22,794
Earnings (loss) per share attributable to IDT Corporation common stockholders:
Basic		$ 0.06	$ 0.04	$ (0.02)	$ 1
Diluted		$ 0.06	$ 0.04	$ (0.02)	$ 0.99
Weighted-average number of shares used in calculation of earnings (loss) per share:
Basic		24,643	22,768	24,635	22,740
Diluted		24,724	22,963	24,635	22,931
Dividends declared per common share		$ 0.19	$ 0.19	$ 0.38	$ 0.38
(i) Stock-based compensation included in selling, general and administrative expenses		$ 987	$ 1,426	$ 1,797	$ 2,128

[1] Stock-based compensation included in selling, general and administrative expenses