Business Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015	Oct. 31, 2014	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Summary of operating results for the business segments
Revenues	$ 167	$ 167	$ 165	$ 159	$ 122	$ 219	$ 112	$ 1,703	$ 2,769	$ 2,867	$ 2,781	$ 4,823	$ 658	$ 2,156	$ 13,240
Income (loss) from operations													(43,011)	(9,087)	266
Straight Path Spectrum [Member]
Summary of operating results for the business segments
Revenues													658	461	426
Income (loss) from operations													(34,976)	(5,508)	(1,641)
Straight Path IP Group [Member]
Summary of operating results for the business segments
Revenues														1,695	12,814
Income (loss) from operations													(6,098)	(2,688)	1,907
Straight Path Ventures [Member]
Summary of operating results for the business segments
Revenues
Income (loss) from operations													$ (1,937)	$ (891)