Settlement of Claims with IDT and Sale of Straight Path IP Group (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2017	Oct. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	$ 165	$ 159
Costs and expenses:
Selling, general and administrative	3,241	3,361
Total costs and expenses	3,395	3,562
Loss from operations	(13,230)	(3,403)
Other income (expense):
Interest expense including amortization of debt discounts	836
Interest income	6	7
Total other income (expense)	(830)	29
Loss provision for income taxes	(14,060)	(3,374)
Provision for income taxes	(7)	(7)
Net loss	(15,556)	(4,255)
Net loss from discontinued operations attributable to Straight Path Communications Inc.	(15,327)	(4,131)
Discontinued Straight Path IP Group [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues
Costs and expenses:
Selling, general and administrative	1,294	875
Total costs and expenses	1,294	875
Loss from operations	(1,294)	(875)
Other income (expense):
Interest expense including amortization of debt discounts	(195)
Interest income		2
Total other income (expense)	(195)	2
Loss provision for income taxes	(1,489)	(873)
Provision for income taxes		(1)
Net loss	(1,489)	(874)
Loss attributable to noncontrolling interests	229	124
Net loss from discontinued operations attributable to Straight Path Communications Inc.	$ (1,260)	$ (750)