Subsequent Event - (Schedule of Proforma Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands		Jan. 31, 2017	Jul. 31, 2016	Jan. 31, 2016	Jul. 31, 2015
Assets, Current [Abstract]
Cash and cash equivalents		$ 7,837	$ 11,361	$ 15,350	$ 18,620
Restricted cash
Trade accounts receivable, net		40	40
Inventory		643
Prepaid expenses and other current assets		919	1,627
Total current assets		9,439	13,028
Intangible assets		365	365
Other assets		111	104
Total assets		9,915	13,497
Current liabilities:
Trade accounts payable		1,016	684
Accrued expenses		368	1,042
Loan payable, net of debt discount
FCC consent decree payable		15,000
Deferred revenue		197	73
Income taxes payable		221	225
Total current liabilities		16,802	2,024
Settlement payable - stockholders			7,200
Deferred revenue - long-term portion		80	92
Total liabilities		24,082	2,116
Straight Path Communications Inc. stockholders' equity:
Preferred stock
Additional paid-in capital		26,073	21,589
Accumulated deficit		(37,781)	(8,225)
Treasury stock, value		(428)	(428)
Total Straight Path Communications Inc. stockholders' equity (deficiency)		(12,011)	13,058
Noncontrolling interests		(2,156)	(1,677)
Total equity (deficiency)		(14,167)	11,381
Total liabilities and equity (deficiency)		9,915	13,497
Common Class A [Member]
Straight Path Communications Inc. stockholders' equity:
Common stock value		8	8
Class B Common Stock [Member]
Straight Path Communications Inc. stockholders' equity:
Common stock value		117	$ 114
Pro forma [Member]
Assets, Current [Abstract]
Cash and cash equivalents		10,337
Restricted cash		15,000
Trade accounts receivable, net		40
Inventory		643
Prepaid expenses and other current assets		919
Total current assets		26,939
Intangible assets		365
Other assets		111
Total assets		27,415
Current liabilities:
Trade accounts payable		1,016
Accrued expenses		368
Loan payable, net of debt discount		13,460
FCC consent decree payable		15,000
Deferred revenue		197
Income taxes payable		221
Total current liabilities		30,262
Settlement payable - stockholders		7,200
Deferred revenue - long-term portion		80
Total liabilities		37,542
Straight Path Communications Inc. stockholders' equity:
Preferred stock
Additional paid-in capital		30,113
Accumulated deficit		(37,781)
Treasury stock, value		(428)
Total Straight Path Communications Inc. stockholders' equity (deficiency)		(7,971)
Noncontrolling interests		(2,156)
Total equity (deficiency)		(10,127)
Total liabilities and equity (deficiency)		27,415
Pro forma [Member] | Common Class A [Member]
Straight Path Communications Inc. stockholders' equity:
Common stock value		8
Pro forma [Member] | Class B Common Stock [Member]
Straight Path Communications Inc. stockholders' equity:
Common stock value		117
Historical [Member] | Common Class A [Member]
Straight Path Communications Inc. stockholders' equity:
Common stock value		8
Historical [Member] | Class B Common Stock [Member]
Straight Path Communications Inc. stockholders' equity:
Common stock value		117
Proforma Adjustments [Member]
Assets, Current [Abstract]
Cash and cash equivalents	[1]	2,500
Restricted cash	[1]	15,000
Trade accounts receivable, net
Inventory
Prepaid expenses and other current assets
Total current assets		17,500
Intangible assets
Other assets
Total assets		17,500
Current liabilities:
Trade accounts payable
Accrued expenses
Loan payable, net of debt discount	[1]	17,500
Warrants issued under loan agreement	[2]	(4,040)
FCC consent decree payable
Deferred revenue
Income taxes payable
Total current liabilities		13,460
Settlement payable - stockholders
Deferred revenue - long-term portion
Total liabilities		13,460
Straight Path Communications Inc. stockholders' equity:
Preferred stock
Common stock value
Additional paid-in capital	[2]	4,040
Accumulated deficit
Treasury stock, value
Total Straight Path Communications Inc. stockholders' equity (deficiency)		4,040
Noncontrolling interests
Total equity (deficiency)		4,040
Total liabilities and equity (deficiency)		17,500
Proforma Adjustments [Member] | Common Class A [Member]
Straight Path Communications Inc. stockholders' equity:
Common stock value
Proforma Adjustments [Member] | Class B Common Stock [Member]
Straight Path Communications Inc. stockholders' equity:
Common stock value

[1] (A) To record the proceeds from the Loan Agreement. According to the terms of the Loan Agreement, $15 million of the Loan Amount will be used to pay the Initial Civil Penalty. As such, $15 million has been classified as restricted cash.

[2] (B) To record the value of the warrants issued under the Loan Agreement. The value of the warrants will be amortized to interest expense over the term of the Loan Agreement.