Sale of Interest in Fabrix Systems Ltd. (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2015	Apr. 30, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (loss) before income taxes	$ 1,064	$ 9,194	$ 86,566	$ 20,517
Fabrix Subsidiary [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (loss) before income taxes		296	917	(1,380)
Income (loss) before income taxes attributable to IDT Corporation		$ 261	$ 1,325	$ (1,221)