IDT Financial Services Holding Limited Assets and Liabilities Held for Sale (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 before income taxes	$ (2,201)	$ (6,614)	$ (2,405)	$ 4,282
IDT Financial Services Holding Limited [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss before income taxes	(3)	(631)	(1,012)	(457)
Loss before income taxes attributable to IDT Corporation	$ (3)	$ (631)	$ (1,012)	$ (457)