Other Operating Expense, Net (Details 1) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2020	Jan. 31, 2019
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other operating expense, net	$ (392)	$ (2,090)	$ (3,168)	$ (3,385)
Provision for income taxes	(1,164)	(1,236)	(1,700)	(2,176)
Net income (loss)	904	(1,011)	(518)	(3,009)
Net income (loss) attributable to IDT Corporation	$ 932	$ (1,311)	$ (581)	$ (3,610)
Earnings (loss) per share attributable to IDT Corporation common stockholders:
Basic	$ 0.04	$ (0.05)	$ (0.02)	$ (0.15)
Diluted	$ 0.04	$ (0.05)	$ (0.02)	$ (0.15)
Error Correction [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other operating expense, net		$ (2,000)		$ (3,100)
Provision for income taxes		500		750
Net income (loss)		(1,500)		(2,350)
Net income (loss) attributable to IDT Corporation		$ (1,500)		$ (2,350)
Earnings (loss) per share attributable to IDT Corporation common stockholders:
Basic		$ (0.06)		$ (0.10)
Diluted		$ (0.06)		$ (0.10)
Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other operating expense, net		$ (90)		$ (285)
Provision for income taxes		(1,736)		(2,926)
Net income (loss)		489		(659)
Net income (loss) attributable to IDT Corporation		$ 189		$ (1,260)
Earnings (loss) per share attributable to IDT Corporation common stockholders:
Basic		$ 0.01		$ (0.05)
Diluted		$ 0.01		$ (0.05)
As Adjusted [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other operating expense, net		$ (2,090)		$ (3,385)
Provision for income taxes		(1,236)		(2,176)
Net income (loss)		(1,011)		(3,009)
Net income (loss) attributable to IDT Corporation		$ (1,311)		$ (3,610)
Earnings (loss) per share attributable to IDT Corporation common stockholders:
Basic		$ (0.05)		$ (0.15)
Diluted		$ (0.05)		$ (0.15)