Other Operating Expense, Net (Details 1) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Oct. 31, 2019	Oct. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other operating expense	$ (2,775)	$ (1,295)
Provision for income taxes	536	939
Net loss	(1,422)	(1,998)
Net loss attributable to IDT Corporation	$ (1,513)	(2,299)
Error Correction [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other operating expense		(1,100)
Provision for income taxes		250
Net loss		(850)
Net loss attributable to IDT Corporation		$ (850)
Loss per share attributable to IDT Corporation common stockholders:
Basic		$ (0.04)
Diluted		$ (0.04)
Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other operating expense		$ (195)
Provision for income taxes		(1,189)
Net loss		(1,148)
Net loss attributable to IDT Corporation		$ (1,449)
Loss per share attributable to IDT Corporation common stockholders:
Basic		$ (0.06)
Diluted		$ (0.06)
As Adjusted [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other operating expense		$ (1,295)
Provision for income taxes		(939)
Net loss		(1,998)
Net loss attributable to IDT Corporation		$ (2,299)
Loss per share attributable to IDT Corporation common stockholders:
Basic		$ (0.10)
Diluted		$ (0.10)