No definition available.

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

- Definition

Reduction in noncontrolling interest.

+ References

No definition available.

+ Details

Name:	IDT_NoncontrollingInterestDecreaseFromPurchaseOfEquity
Namespace Prefix:	IDT_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

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

Amount of other increase (decrease) in additional paid in capital (APIC).

+ References

No definition available.

+ Details

Name:	us-gaap_AdjustmentsToAdditionalPaidInCapitalOther
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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:	dtr-types: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

- Definition

Amount of liability recognized arising from contingent consideration in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 35
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=116859824&loc=d3e6819-128478

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

+ Details

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

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

+ Details

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

- 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:

- Details

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

Acquisitions (Details Narrative) - USD ($)					12 Months Ended
Acquisitions (Details Narrative) - USD ($)	Jun. 15, 2021	Mar. 22, 2021	Dec. 03, 2020	Dec. 11, 2019	Jul. 31, 2021
Restructuring Cost and Reserve [Line Items]
Reduction in additional paid in capital	$ 300,000
IDT International Telecom, Inc [Member]
Restructuring Cost and Reserve [Line Items]
Business acquired percentage	19.00%		51.00%
Contingent consideration, 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
Purchase price	$ 1,000,000.0		$ 2,732,000
Contingent consideration	300,000
Fair value of contingent consideration	200,000
Reduction in noncontrolling interest	$ 1,000,000.0
IDT International Telecom, Inc [Member] \| Noncontrolling Interest [Member]
Restructuring Cost and Reserve [Line Items]
Purchase of option shares reduction		200,000
Purchase of option shares reduction		(200,000)
IDT International Telecom, Inc [Member] \| Additional Paid-in Capital [Member]
Restructuring Cost and Reserve [Line Items]
Purchase of option shares reduction		(21,000)
Purchase of option shares reduction		$ 21,000
IDT International Telecom, Inc [Member] \| Put/Call Option Agreement [Member]
Restructuring Cost and Reserve [Line Items]
Business acquired percentage			5.00%
Net2phone, Inc. [Member]
Restructuring Cost and Reserve [Line Items]
Business acquired percentage				100.00%
Ringsouth Europa SL [Member]
Restructuring Cost and Reserve [Line Items]
Contingent consideration, description					The contingent consideration includes two potential payments to the seller of $0.4 million each, based on monthly recurring revenue targets to be achieved over a 36-month period and 48-month period.
Purchase price				$ 450,000