Rafael Holdings, Inc. Spin-Off (Details 1) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
(Loss) income before income taxes	$ (2,201)	$ (6,614)	$ (2,405)	$ 4,282
Rafael Holdings, Inc. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
(Loss) income before income taxes	(1,190)	52	(2,410)	375
(Loss) income before income taxes attributable to IDT Corporation	$ (1,062)	$ 52	$ (2,107)	$ 375