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.