The exercise price of the open option contracts written on the investment.

No definition available.

Name:	IDT_OpenOptionContractWrittenExercisePrice
Namespace Prefix:	IDT_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Purchase of option shares reduction.

+ References

No definition available.

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

For contingent consideration arrangements recognized in connection with a business combination, this element represents a description of such arrangements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479

+ Details

Name:	us-gaap_BusinessCombinationContingentConsiderationArrangementsDescription
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

For contingent consideration arrangements recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the consideration which may be paid.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479

+ Details

Name:	us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_BusinessAcquisitionAxis=IDT_IDTInternationalTelecomIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_NoncontrollingInterestMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_AdditionalPaidInCapitalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_OptionIndexedToIssuersEquityTypeAxis=IDT_PutCallOptionAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=IDT_NetTwoPhoneIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Acquisitions (Details Narrative) - USD ($)		9 Months Ended
Acquisitions (Details Narrative) - USD ($)	Mar. 22, 2021	Apr. 30, 2021	Dec. 03, 2020	Dec. 11, 2019
IDT International Telecom, Inc [Member]
Business Acquisition [Line Items]
Business acquired percentage			51.00%
Business Combination, Contingent Consideration Arrangements, Description		The contingent consideration of $0.5 million will be paid (a) no later than November 30, 2021 if the acquired company generates EBITDA (as defined in the purchase agreement) of no less than $1.0 million between October 1, 2020 and September 30, 2021; or (b) no later than November 30, 2022 if the acquired company generates EBITDA of no less than $1.0 million between October 1, 2021 and September 30, 2022.
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High			$ 500,000
Option of shares value	$ 300,000
IDT International Telecom, Inc [Member] \| Noncontrolling Interest [Member]
Business Acquisition [Line Items]
Purchase of option shares reduction	200,000
IDT International Telecom, Inc [Member] \| Additional Paid-in Capital [Member]
Business Acquisition [Line Items]
Purchase of option shares reduction	$ 21,000
IDT International Telecom, Inc [Member] \| Put/Call Option Agreement [Member]
Business Acquisition [Line Items]
Business acquired percentage			5.00%
Net2phone, Inc. [Member]
Business Acquisition [Line Items]
Business acquired percentage				100.00%