Schedule of Unrealized (losses) Gains for All Equity Investments (Details) - USD ($) $ in Thousands	12 Months Ended
Jul. 31, 2021	Jul. 31, 2020
Equity Investments
Net gains (losses) recognized during the period on equity investments	$ 8,830	$ (336)
Less: net gains recognized during the period on equity investments redeemed during the period	1,090
Unrealized gains (losses) recognized during the period on equity investments still held at the reporting date	$ 7,740	$ (336)

Amount of recognized unrealized gain (loss) net on equity securities held (FV-NI).

No definition available.

Name:	IDT_EquitySecuritiesFvNiRecognizedUnrealizedGainLossNetEquitySecuritiesHeld
Namespace Prefix:	IDT_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration