Stock-Based Compensation (Details Textual)									1 Months Ended								3 Months Ended												12 Months Ended
	Apr. 04, 2016 shares	Mar. 15, 2016 USD ($) shares	Jan. 05, 2016 USD ($) Directors shares	Jan. 05, 2015 USD ($) Directors shares	Sep. 01, 2014 USD ($) shares	Jul. 30, 2014 USD ($) shares	Aug. 06, 2013 USD ($) shares	Aug. 01, 2013 USD ($) shares	Jun. 30, 2016 $ / shares shares	Oct. 31, 2015 USD ($) shares	Jul. 23, 2015 USD ($) Directors shares	May 31, 2014	Jan. 31, 2014 USD ($) shares	May 31, 2013	Apr. 15, 2013 USD ($)	May 31, 2011 USD ($)	Jul. 31, 2016 USD ($) $ / shares	Apr. 30, 2016 USD ($)	Jan. 31, 2016 USD ($)	Oct. 31, 2015 USD ($)	Jul. 31, 2015 USD ($)	Apr. 30, 2015 USD ($)	Jan. 31, 2015 USD ($)	Oct. 31, 2014 USD ($)	Jul. 31, 2014 USD ($) $ / shares shares	Apr. 30, 2014 USD ($)	Jan. 31, 2014 USD ($)	Oct. 31, 2013 USD ($) shares	Jul. 31, 2016 USD ($) $ / shares shares	Jul. 31, 2015 USD ($) $ / shares	Jul. 31, 2014 USD ($) $ / shares shares	Jul. 31, 2013 USD ($) $ / shares shares	Jul. 31, 2012 USD ($)	Oct. 08, 2015 shares
Stock-Based Compensation (Textual)
Common stock available for grant of awards by an additional shares | shares
Exercise option price per share | $ / shares																	$ 4.41								$ 0				$ 4.41		$ 0
Expected volatility																													65.60%
Discount rate																													0.65%
Expected term																													1 year 9 months 18 days
Stock-based compensation																													$ 32,000		$ 12,000
Intrinsic value of options exercised																													$ 45,727	$ 203,640	$ 13,195
Closing stock price | $ / shares																													$ 18.24	$ 23.57	$ 9.87
Selling, general and administrative																	$ 3,538,000	$ 1,528,000	$ 2,346,000	$ 1,612,000	$ 2,870,000	$ 1,353,000	$ 1,605,000	$ 1,103,000	$ 725,000	$ 665,000	$ 1,042,000	$ 569,000	$ 9,024,000	$ 6,931,000	$ 3,001,000
Unrecognized compensation cost related to non-vested restricted share value																	2,300,000												2,300,000
Unrecognized compensation cost in fiscal 2017																													1,470,000
Unrecognized compensation cost in fiscal 2018																													707,000
Unrecognized compensation cost in fiscal 2019																													127,000
Fair value of stock options																													$ 32,233	0	0
Unrecognized compensation cost recognize over a period																													11 months 1 day
Percentage of stock option to purchase of outstanding common stock, description															A consultant was granted a stock option to purchase up to 0.5% of the outstanding shares of common stock of Straight Path IP Group.
Stock Option [Member]
Stock-Based Compensation (Textual)
Selling, general and administrative																													$ 2,770,000	$ 3,350,000	$ 758,000
Unrecognized compensation cost related to non-vested restricted share value																	$ 355,000												$ 355,000
IDT[Member]
Stock-Based Compensation (Textual)
Common stock options purchase | shares																																641,567
Common stock shares outstanding option, percentage																																10.00%
Straight Path IP Group [Member]
Stock-Based Compensation (Textual)
Estimated value of grant option Straight Path IP															$ 13,318
Consultant stock option vested percentage												33.40%		33.40%	33.20%
Expected volatility															51.00%
Discount rate															0.80%
Expected term															4 years
Stock-based compensation																																$ 13,000,000	$ 52,000,000
Straight Path IP Group [Member] | Former CEO [Member]
Stock-Based Compensation (Textual)
Estimated value of grant option Straight Path IP																$ 200,000
Stock option purchase of consultant, percentage																5.00%
Grant options equity outstanding of Straight Path IP																$ 400,000
Expected volatility																49.00%
Discount rate																2.20%
Expected term																6 years
Common Class B [Member]
Stock-Based Compensation (Textual)
Common stock shares reserved | shares																																678,532
Common stock available for grant of awards by an additional shares | shares																												350,000
Common stock options purchase | shares																																32,155
Exercise option price per share | $ / shares																																$ 5.67
Number of share granted for service | shares							10,100																								5,500
Common stock with aggregate fair value						$ 1,214,000	$ 50,000	$ 1,519,000																							$ 91,000
Restricted common stock shares description						One-third of both grants of restricted shares vested on March 30, 2015 and the remaining vest as to approximately one-third of the granted shares on each of February 1, 2016 and 2017.	These restricted shares vest as to one-third of the granted shares in each of August 2014, 2015 and 2016.																								These restricted shares vested as to one-half of the granted shares on each of January 31, 2015 and July 31, 2015.
Restricted common stock non vested -shares | shares																													257,584
Common Class B [Member] | 2013 Plan [Member]
Stock-Based Compensation (Textual)
Common stock available for grant of awards by an additional shares | shares																																		475,000
Common Class B [Member] | Restricted Stock [Member]
Stock-Based Compensation (Textual)
Restricted shares, granted | shares		8,000
Number of restricted shares issued, value		$ 285,000
Common Class B [Member] | Officer [Member]
Stock-Based Compensation (Textual)
Expected term									3 years
Options vested period									1 year
Common Class B [Member] | Jonathan Rand [Member]
Stock-Based Compensation (Textual)
Number of share granted for service | shares						52,000		38,268
Common Class B [Member] | Davidi Jonas [Member]
Stock-Based Compensation (Textual)
Number of share granted for service | shares						71,000		229,608			60,000
Common stock with aggregate fair value											$ 1,494,900
Common Class B [Member] | Non Employee Director [Member]
Stock-Based Compensation (Textual)
Number of directors | Directors			3	3
Number of share granted for service | shares			24,000	24,000				3,750					24,000
Common stock with aggregate fair value			$ 418,000	$ 438,000				$ 21,263					$ 197,000
Common Class B [Member] | Two Employees [Member]
Stock-Based Compensation (Textual)
Common stock options purchase | shares									87,707
Exercise option price per share | $ / shares									$ 50.00
Number of directors | Directors											2
Number of share granted for service | shares											22,500
Common stock with aggregate fair value											$ 685,800
Restricted common stock shares description											These restricted shares vest as to one-third of the granted shares on each of October 16, 2015, 2016 and 2017.
Common Class B [Member] | One Employee [Member]
Stock-Based Compensation (Textual)
Number of directors | Directors											1
Number of share granted for service | shares											5,000
Common stock with aggregate fair value											$ 152,400
Restricted common stock shares description											These restricted shares vest as to one-half of the granted shares on each of October 16, 2016 and 2017.
Common Class B [Member] | Jerry Pi [Member]
Stock-Based Compensation (Textual)
Number of share granted for service | shares					60,000						30,000
Common stock with aggregate fair value					$ 573,000						$ 914,400
Restricted common stock shares description					These restricted shares originally vested as to one-third of the granted shares on each of October 16, 2015, September 1, 2016 and September 1, 2017. On June 2, 2016, the vesting for the second traunche was changed from September 1, 2016 to October 16, 2016 and the vesting for the third traunche was changed from September 1, 2017 to October 16, 2017.						These restricted shares vest as to one-third of the granted shares on each of October 16, 2016, 2017 and 2018.
Common Class B [Member] | Employee [Member]
Stock-Based Compensation (Textual)
Number of share granted for service | shares	4,000									28,000
Common stock with aggregate fair value										$ 1,052,000
Restricted common stock shares description										The balance of the shares will vest as to one-third of the granted shares on each of October 16, 2016, 2017 and 2018.
Common Class B [Member] | Employee [Member] | October 16, 2016 [Member] | Restricted Stock [Member]
Stock-Based Compensation (Textual)
Restricted shares, Vested | shares		4,000
Common Class B [Member] | Employee [Member] | March 16, 2017 [Member] | Restricted Stock [Member]
Stock-Based Compensation (Textual)
Restricted shares, Vested | shares		4,000